Viscous fluid transfer apparatus and transfer method, electronic component mounting apparatus and mounting method, and semiconductor device

ABSTRACT

A squeegee unit having a stirring squeegee and a leveling squeegee fixed thereto is rocked with the reciprocating operation of a transfer unit moving mechanism to cause the stirring squeegee and the leveling squeegee to approach the pan surface of a transfer unit on going and returning paths. Consequently, the stirring squeegee stirs a viscous fluid put on the transfer unit on the going path of the transfer unit and the leveling squeegee uniformly flattens the viscous fluid stirred on the going path to have a predetermined thickness on the returning path of the transfer unit, thereby forming a flat viscous fluid transfer surface on the transfer unit. By immersing the terminal portion of the electronic component in the viscous fluid transfer surface, the viscous fluid is transferred to the electronic component and the electronic component is then mounted in a predetermined mounting position.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a viscous fluid transferapparatus and method for transferring a viscous fluid to the connectingterminal of a package component such as an IC. The present inventionalso relates to an electronic component mounting apparatus and methodusing the viscous fluid transfer apparatus, and a semiconductor device.Moreover, the present invention particularly relates to athree-dimensional mounting technique for providing an electroniccomponent in plural stages.

[0003] 2. Description of the Related Art

[0004] In the recent electronic apparatus industry, a high functionalityand a reduction in a size and a weight of a product have been vigorouslydeveloped, and various mounting methods such as double-sided mountinghave been employed for an electronic component such as an IC in order toreduce a mounting area to a circuit board in addition to an increase inthe integration of a semiconductor device itself.

[0005] In the package technique of the electronic component, moreover, aDIP (Dual Inline Package) which has conventionally been used widely isswitched to a QFP (Quad Flat Package) and an SOP (Small Outline Package)which have a space between leads as shown in a double-sided mountingstate of FIG. 58(a), and furthermore, attention has been paid to an areaarray type package such as a BGA (Ball Grid Array) or a CSP (Chip SizePackage) shown in FIG. 58(b) as a technique for a practical stage.

[0006] On the other hand, a bare chip mounting method for carrying outdirect mounting onto a circuit board without packaging has also beenpartially employed. However, there has still been a problem to be solvedfor a mass production and a reduction in a cost. In the bare chipmounting method, a flux is transferred onto a bare chip component to bemounted on a circuit board. In this case, examples of a flux transferdevice for transferring the flux include a device for forming thetransfer surface of the flux by reciprocating a squeegee 512 havingalmost the same structure over a transfer unit 510 as shown in FIGS.59(a), 59(b), 60(a), and 60(b). The bare chip component is mounted bymoving the squeegee 512 over the transfer unit 510 to extend the fluxover the whole pan surface and immersing the bare chip component on theextended flux to transfer the flux to the component side, and bypressure welding the bare chip component into a predetermined positionon the circuit board after the transfer.

[0007] Moreover, there have been various methods for mounting theelectronic component of the area array type package onto the circuitboard, and the mounting can be carried out in the following manner, forexample. First of all, a land is formed in a position on the circuitboard corresponding to the solder ball of an electronic component (BGA)and a solder cream is mask printed on the land. Then, the electroniccomponent is mounted in the predetermined position on the circuit boardto superpose the printed solder cream on the solder ball of theelectronic component, and the electronic component is temporarily fixedto the circuit board with the viscosity of the solder cream. The circuitboard is subjected to a reflow process so that the solder cream and thesolder ball are molten and the land and the solder ball of theelectronic component are connected and fixed to each other.

[0008] In the mounting method for the electronic component of theconventional area array type package, however, a reduction in a mountingarea has further been required. And furthermore, a mask hole formingtechnique having high precision for a solder cream printing screen and amask aligning technique have been required with an enhancement in thefine pitch of the electronic component. For this reason, stable mountinghaving high precision has been restricted over the extension of acurrent method and it is inevitably hard to carry out further highdensity mounting so that the development of other different mountingmethods has been desired.

[0009] A technique for forming an electronic component with a stackstructure having several stages has variously been investigated.However, the electronic component is not simply stacked but a jigaccommodating the electronic component therein is provided or a contactstructure is very complicated. Consequently, there has been a problem inthat the design of a conventional circuit pattern is forcibly changedconsiderably and a mounting cost is hard to reduce.

[0010] Moreover, it has also been supposed that the electronic componentis three-dimensionally mounted by stack on a rear face opposite to themounting surface side of the electronic component for an area array typepackage such as a BGA or a CSP having the small pitch of a connectingterminal. There has been a problem in that a method of giving a soldercream for the stack is to be established or alignment precision is to bemaintained. Therefore, the practical use has not been attained.

[0011] When a solder cream is to be put and transferred onto theelectronic component in place of the flux by using the flux transferdevice for transferring the flux onto the bare chip component, theviscosity of the solder cream is extremely higher than that of the flux.Therefore, the solder cream overflows from the transfer unit so that theflux transfer device cannot be actually substituted for solder creamtransfer.

[0012] FIGS. 59(a), 59(b), 60(a) and 60(b) show a state in which thesolder cream is put onto the flux transfer device to move the squeegee512, (a) being a plan view and (b) being a side view. As shown in FIGS.59(a) and (b), when the squeegee 512 is moved from the left side to theright side in the drawing, the solder cream is protruded from the end inthe longitudinal direction of the squeegee 512 based on a difference ina viscosity so that it overflows from the edge portion of the transferunit 510. In the same manner as in FIGS. 60(a) and (b), when thesqueegee 512 is moved from the right side to the left side in thedrawing, the solder cream further overflows.

[0013] In addition, the solder cream coming in contact as shown in FIG.61 is transmitted toward the upper part of each squeegee 512 due to aviscosity thereof, and finally, the solder cream sticks to each portionof the apparatus and the solder cream is dropped off from a part of theapparatus. As a result, the solder cream is scattered to the surroundingenvironment so that maintenance is often required. Consequently, amanufacturing man-hour is increased and the quality of a product isdeteriorated.

[0014] Moreover, there is also a problem regarding a sucking nozzle 514to be used for the transfer of the solder cream. More specifically, asshown in FIG. 62, when an electronic component 520 is to be pushedagainst an inclined surface, for example, the solder cream is to betransferred to the electronic component 520 by using the transfer unit510 having the inclined pan surface, the sucking nozzle 514 usually hasa sucking tip portion 514 a formed of a metal and the rear face of theelectronic component 520 is inclined. Therefore, a clearance isgenerated between the sucking tip portion 514 a and the rear face of theelectronic component 520 so that air leaks from the clearance andsuction cannot be carried out.

[0015] It can be proposed that a component sucking property can beimproved by attaching a rubber pad 516 to the sucking tip portion 514 a.However, when the solder cream is to be transferred to the electroniccomponent 520 as shown in FIG. 62, for example, the rubber pad 516 iselastically deformed and contracted in the direction of push-in so thata push-in depth cannot be controlled even if the electronic component520 is pushed in from the surface of the solder cream up to apredetermined depth. Thus, if the solder cream cannot be given to theelectronic component necessarily and sufficiently, connection cannot becarried out reliably so that the conduction failures of the electroniccomponent after mounting or mechanical fixing failures might be caused.

[0016] The invention has been made in consideration of the conventionalcircumstances. It is the first object of the invention to provide aviscous fluid transfer apparatus and a transfer method for transferringa viscous fluid to the terminal portion of an electronic component andlaminating an electronic component, in order to increase a spaceefficiency to mount an area array type package component to a circuitboard at a high density.

[0017] Moreover, it is the second object of the invention to provide anelectronic component mounting apparatus and a mounting method oflaminating and mounting an electronic component onto a circuit board byusing the viscous fluid transfer apparatus and the transfer method.

[0018] Furthermore, it is the third object of the invention to provide asemiconductor device capable of carrying out high density mounting as astack structure having plural stages.

SUMMARY OF THE INVENTION

[0019] In order to achieve the objects, a first aspect of the inventionis directed to a viscous fluid transfer apparatus for forming a flatviscous fluid transfer surface for transferring a viscous fluid to aconnecting terminal of an electronic component. The viscous fluidtransfer apparatus includes a transfer unit having a planar pan surfacefor putting a viscous fluid thereon, a squeegee unit having a planarstirring squeegee for stirring the viscous fluid put on the pan surface,a planar leveling squeegee for uniformly flattening the viscous fluidthus stirred, and a squeegee fixing member serving to separate thesqueegees from each other and to fix them in parallel and having bothends rockably supported pivotally above the transfer unit, a transferunit moving mechanism for reciprocating the transfer unit such that thesqueegee is relatively moved along the pan surface of the transfer unit,and a squeegee driving mechanism for rocking the squeegee unit such thatthe stirring squeegee and the leveling squeegee approach the pan surfaceon going and returning paths, respectively.

[0020] The viscous fluid transfer apparatus rocks the squeegee unithaving the stirring squeegee and the leveling squeegee fixed theretowith the reciprocating operation of the transfer unit moving mechanismthrough the squeegee driving mechanism, and to cause the stirringsqueegee and the leveling squeegee to approach the pan surface of thetransfer unit on going and returning paths, respectively. Consequently,the stirring squeegee stirs the viscous fluid over the transfer unit onthe going path of the transfer unit and the leveling squeegee causes theviscous fluid stirred on the going path to uniformly have apredetermined thickness on the returning path of the transfer unit. As aresult, the flat viscous fluid transfer surface is formed on thetransfer unit.

[0021] A second aspect of the invention is directed to the viscous fluidtransfer apparatus, further including a protrusion formed on a pansurface side of both ends in the longitudinal direction of the stirringsqueegee, wherein the protrusion scrapes the viscous fluid put on thepan surface toward a central side in a longitudinal direction of thestirring squeegee.

[0022] In the viscous fluid transfer apparatus, when the stirringsqueegee is relatively moved again after the leveling squeegee isrelatively moved, the viscous fluid overflowing from both ends in thelongitudinal direction of the leveling squeegee during the relativemovement of the leveling squeegee at the last time can be scraped towardthe central side in the longitudinal direction of the squeegee through aformed discharge portion. Thus, the viscous fluid can be prevented fromoverflowing from the pan surface of the transfer unit.

[0023] A third aspect of the invention is directed to the viscous fluidtransfer apparatus, wherein the protrusion of the stirring squeegee hasa taper face inclined in such a direction as to narrow a passage for theviscous fluid rearward from a front part in a direction of progress ofthe squeegee within a thickness of the squeegee.

[0024] In the viscous fluid transfer apparatus, the protrusion of thestirring squeegee has the taper face for reducing the flow of theviscous fluid. Consequently, the viscous fluid can be scraped toward thecentral side in the longitudinal direction of the squeegee along thetaper face by the relative movement of the stirring squeegee on thetransfer unit and the viscous fluid can overflow from the pan surface ofthe transfer unit with a simple structure.

[0025] A fourth aspect of the invention is directed to the viscous fluidtransfer apparatus, further including an intermediate protrusion formedbetween the protrusions on both ends of the stirring squeegee, whereinthe intermediate protrusion forms the viscous fluid put on the pansurface like a band.

[0026] In the viscous fluid transfer apparatus, the intermediateprotrusion is formed between the protrusions. Consequently, when thestirring squeegee is relatively moved over the transfer unit, theviscous fluid is partially scraped by the intermediate protrusion. As aresult, the viscous fluid is formed like a band over the transfer unit.Consequently, the viscous fluid is scraped from the lower surface of thetransfer unit so that the stirring effect can be enhanced. When the nextleveling squeegee is relatively moved, the viscous fluid formed like aband is flattened to have a uniform thickness so that an excellentviscous fluid transfer surface can always be obtained.

[0027] A fifth aspect of the invention is directed to the viscous fluidtransfer apparatus, wherein the intermediate protrusion has a taper faceinclined in such a direction as to narrow the passage for the viscousfluid rearward from the front part in the direction of progress of thesqueegee within the thickness of the squeegee.

[0028] In the viscous fluid transfer apparatus, the intermediateprotrusion has the taper face inclined in such a direction as to narrowthe passage for the viscous fluid. Consequently, the viscous fluid isscraped along the taper face during the relative movement of thestirring squeegee so that the viscous fluid can be prevented fromoverflowing from the pan surface of the transfer unit.

[0029] A sixth aspect of the invention is directed to the viscous fluidtransfer apparatus, wherein a concave sectional curved portion and aconvex sectional curved portion are sequentially formed on the pansurface side of the leveling squeegee from the front part in thedirection of progress of the squeegee.

[0030] In the viscous fluid transfer apparatus, when the levelingsqueegee is relatively moved, the viscous fluid on the transfer unit ispressurized and extended in the tip portion of the convex sectionalcurved portion, and furthermore, the excessive viscous fluid is rolledin the concave sectional curved portion and is returned in the directionof progress of the squeegee. Consequently, it is possible to prevent theviscous fluid from being transmitted toward the upper part of thesqueegee.

[0031] A seventh aspect of the invention is directed to the viscousfluid transfer apparatus, wherein a tip on the pan surface side of theleveling squeegee is formed to have a V-shaped section.

[0032] In the viscous fluid transfer apparatus, the tip on the pansurface side of the leveling squeegee is formed to have a V sectionwhich can easily be processed. Consequently, the shape of the tipportion of the squeegee can be simplified to reduce the manufacturingcost of the squeegee itself.

[0033] An eighth aspect of the invention is directed to the viscousfluid transfer apparatus, further including a corner portion formed inthe middle of a inclined surface on a part in a direction of progress ofthe leveling squeegee, wherein the corner portion is protruded outwardand formed over a longitudinal direction of the leveling squeegee, andwherein a section of the corner portion is an obtuse angle.

[0034] In the viscous fluid transfer apparatus, the corner portion isformed in the middle of the inclined surface of the leveling squeegee.Consequently, even if the viscous fluid is transmitted upward from thetip portion of the squeegee during the relative movement of the levelingsqueegee, it falls down and is returned at the formed corner portion.Consequently, the viscous fluid can be prevented from excessivelysticking to the squeegee.

[0035] A ninth aspect of the invention is directed to the viscous fluidtransfer apparatus, further including a pressure generating memberprovided in the longitudinal direction of the leveling squeegee in thevicinity of a tip on the pan surface side at the front part in thedirection of progress of the squeegee, wherein the pressure generatingmember forms a narrow path through which the viscous fluid flows betweenthe pan surface and the pressure generating member, while the squeegeeis moving.

[0036] In the viscous fluid transfer apparatus, the pressure generatingmember is provided in the vicinity of the tip on the pan surface side atthe front part in the direction of progress of the leveling squeegee.Consequently, the narrow path is formed between the pressure generatingmember and the pan surface. Therefore, the viscous fluid flowing betweenthe pressure generating member and the pan surface is maintained in ahigh pressure state. Consequently, even if a squeegee speed is high, theviscous fluid can be stably put on the pan surface in a predeterminedthickness.

[0037] A tenth aspect of the invention is directed to the viscous fluidtransfer apparatus, wherein a length of the stirring squeegee is equalto or greater than a scraping width of the leveling squeegee.

[0038] In the viscous fluid transfer apparatus, the stirring squeegeehas a length which is equal to or greater than the scraping width of theleveling squeegee. Consequently, when the stirring squeegee isrelatively moved over the transfer unit, a scraping track can becompletely scraped by the leveling squeegee and the viscous fluid can bestirred without overflowing from the transfer unit.

[0039] An eleventh aspect of the invention is directed to the viscousfluid transfer apparatus, further including a stepped portion providedon the pan surface of the transfer unit at both ends in a direction ofdelivery of the leveling squeegee in a direction of the movement of thesqueegee, wherein the stepped portion is protruded from the pan surfaceby a predetermined height to support both ends of the leveling squeegeein hanging down.

[0040] In the viscous fluid transfer apparatus, the stepped portionprotruded from the pan surface of the transfer unit by a predeterminedheight is provided. Consequently, both ends of the leveling squeegee aresupported in hanging down so that a clearance for the height of thestepped portion is generated together with the pan surface.Consequently, the viscous fluid having a desirable thickness can be puton the transfer unit by setting the height of the stepped portion to bea desirable height.

[0041] A twelfth aspect of the invention is directed to the viscousfluid transfer apparatus, further including a stepped portion providedon the pan surface side at both ends in the longitudinal direction ofthe leveling squeegee, wherein the stepped portion is protruded by apredetermined height.

[0042] In the viscous fluid transfer apparatus, the stepped portionprotruded by a predetermined height is provided on both ends in thelongitudinal direction of the leveling squeegee. Consequently, when theleveling squeegee is pushed against the transfer unit, the steppedportion on both ends of the squeegee contacts on the pan surface of thetransfer unit so that a clearance for the height of the stepped portionis generated together with the pan surface in a region other than bothends of the squeegee. Therefore, the viscous fluid having a desirablethickness can be put on the transfer unit by setting the height of thestepped portion to be a desirable height.

[0043] A thirteenth aspect of the invention is directed to the viscousfluid transfer apparatus, wherein the squeegee driving mechanismincludes a rocking arm having one of ends fixed to a rocking centershaft of the squeegee fixing member and the other end connected to ahorizontal driving mechanism for rocking the squeegee fixing member, andan arm stopper for contacting on the rocking arm to control a rockingangle of the rocking arm.

[0044] In the viscous fluid transfer apparatus, the rocking arm has oneof ends fixed to the rocking center shaft of the squeegee fixing memberand the other end connected to a horizontal driving mechanism forrocking the squeegee fixing member. Consequently, the squeegee fixingmember can be rocked around the rocking center shaft. Thus, the stirringsqueegee and the leveling squeegee can be caused to alternately approachthe transfer unit. Moreover, the arm stopper is provided to contact onthe rocking arm at a predetermined rocking angle. Therefore, the rockingangle of the rocking arm can be controlled and the contact position ofthe arm stopper on the rocking arm can be regulated so that the heightsof the squeegee and the transfer unit surface can be controlled finely.

[0045] A fourteenth aspect of the invention is directed to the viscousfluid transfer apparatus further including, a V block holding thesqueegee fixing member on the end the of the squeegee fixing member, anda table having a projection and supporting the squeegee fixing member onthe other end side of the squeegee fixing member by the projection,wherein the squeegee fixing member including a cylindrical pin in anaxial direction to one of end side in a longitudinal direction of thesqueegee fixing member, and an engagement portion having a key grooveparallel with the axial direction is provided on the other end side ofthe squeegee fixing member, wherein the projection engaged with the keygroove, and wherein the squeegee unit is supported removably by the Vblock, the table and the squeegee fixing member.

[0046] In the viscous fluid transfer apparatus, the squeegee fixingmember has the pin connected to one of end sides in the longitudinaldirection and the engagement portion having the key groove provided onthe other end side. Consequently, the squeegee fixing member has one ofthe end sides thereof held by the V block and the other end supported onthe formed table of the projection, thereby supporting the squeegeeunit. Therefore, the squeegee unit can be removably supported and thesqueegee fixing member can be prevented from being twisted, therebyenhancing the reproducibility of the attachment position. Accordingly,even if the squeegee unit is removed when cleaning the squeegee unit, itcan be easily attached to an accurate position again so that maintenancecan be enhanced.

[0047] A fifteenth aspect of the invention is directed to a viscousfluid transfer apparatus for forming a flat viscous fluid transfersurface for transferring a viscous fluid to a connecting terminal of anelectronic component, including a belt conveyer having a planar beltsurface on which the viscous fluid is to be put, a squeegee foruniformly flattening the viscous fluid put on the belt surface by adelivery operation of the belt conveyer, and a stirring mechanismprovided in a front stage of the squeegee in a direction of delivery ofthe belt conveyer and serving to stir the viscous fluid on the beltsurface.

[0048] In the viscous fluid transfer apparatus, after the viscous fluidput on the belt surface of the belt conveyer is stirred by the stirringmechanism, it is uniformly flattened over the belt surface through thesqueegee with the delivery operation of the belt conveyer. Therefore,the viscous fluid transfer surface can be formed continuously.Consequently, a new viscous fluid transfer surface can always be exposedcontinuously.

[0049] A sixteenth aspect of the invention is directed to a viscousfluid transfer method of forming a flat viscous fluid transfer surfaceby a squeegee and immersing a terminal portion of an electroniccomponent in the viscous fluid transfer surface, thereby transferring aviscous fluid to the electronic component, wherein the viscous fluid isput on a transfer unit having a flat pan surface, a plate-shapedstirring squeegee is relatively moved with respect to the pan surface ina forward direction, thereby stirring the viscous fluid, and aplate-shaped leveling squeegee is then moved relatively with respect tothe pan surface in a reverse direction, thereby uniformly flattening thestirred viscous fluid on the transfer unit to form a viscous fluidtransfer surface.

[0050] In the viscous fluid transfer method, the viscous fluid put onthe transfer unit is stirred by relatively moving the stirring squeegeeover the pan surface in a forward direction and the viscous fluid thusstirred is then flattened uniformly by relatively moving the levelingsqueegee over the pan surface in a reverse direction, thereby forming aflat viscous fluid transfer surface, and the terminal portion of theelectronic component is immersed in the viscous fluid transfer surfaceto transfer the viscous fluid to the electronic component. By relativelymoving the two squeegees alternately, thus, the flat viscous fluidtransfer surface can be formed stably and the viscous fluid can beuniformly transferred to the terminal portion of the electroniccomponent.

[0051] A seventeenth aspect of the invention is directed to the viscousfluid transfer method, wherein when the leveling squeegee is relativelymoved and the stirring squeegee is then moved relatively again in aforward direction, the viscous fluid overflowing from both ends in alongitudinal direction of the leveling squeegee during the relativemovement of the leveling squeegee is scraped toward a central side inthe longitudinal direction of the squeegee during the relative movementof the stirring squeegee.

[0052] In the viscous fluid transfer method, the viscous fluidoverflowing from both ends in the longitudinal direction of the levelingsqueegee is scraped toward the central side in the longitudinaldirection of the squeegee during the relative movement of the stirringsqueegee. Consequently, the viscous fluid can be prevented fromoverflowing from the transfer unit and the stirring squeegee and theleveling squeegee can be relatively moved continuously without causingthe viscous fluid to overflow from the transfer unit.

[0053] An eighteenth aspect of the invention is directed to the viscousfluid transfer method, wherein a thickness of the viscous fluid transfersurface to be formed on the transfer unit is set by regulating a heightof a rise from the pan surface of the transfer unit of the levelingsqueegee.

[0054] In the viscous fluid transfer method, the thickness of theviscous fluid transfer surface to be formed on the transfer unit can beoptionally set by regulating a rising height from the pan surface of thetransfer unit of the leveling squeegee.

[0055] A nineteenth aspect of the invention is directed to the viscousfluid transfer method, wherein the height of the rise from the pansurface is regulated by causing the leveling squeegee to contact on thepan surface of the transfer unit over a whole width and setting aposition of the contact to be a reference height.

[0056] In the viscous fluid transfer method, first of all, the levelingsqueegee is caused to contact on the pan surface of the transfer unitover the whole width, thereby holding the leveling squeegee in parallelwith the pan surface. Then, the position of the contact is set to be thereference height and the leveling squeegee is raised by a predeterminedheight from the reference height, thereby regulating the rising heightfrom the pan surface. Consequently, the degree of parallelism of theleveling squeegee and the pan surface can be increased so that therising height can be regulated with a high degree of parallelismmaintained. Accordingly, the thickness of the viscous fluid transfersurface can be made uniform with high precision.

[0057] A twentieth aspect of the invention is directed to the viscousfluid transfer method, wherein the thickness of the viscous fluidtransfer surface is set by a height of a stepped portion provided on thepan surface side on both ends in the longitudinal direction of theleveling squeegee.

[0058] In the viscous fluid transfer method, when the protrusion heightof the stepped portion provided on both ends in the longitudinaldirection of the leveling squeegee is set to be a predetermined heightto cause the stepped portion of the leveling squeegee to contact on thepan surface of the transfer unit, the clearance generated between theleveling squeegee and the pan surface in a region other than both endsof the squeegee is set corresponding to the protrusion height of thestepped portion and the thickness of the formed viscous fluid transfersurface is set. Consequently, the thickness of the height of the steppedportion provided in the leveling squeegee is automatically set withoutrequiring a regulating work.

[0059] A twenty-first aspect of the invention is directed to a viscousfluid transfer method of forming a flat viscous fluid transfer surfaceby a squeegee and immersing a terminal portion of an electroniccomponent in the viscous fluid transfer surface, thereby transferring aviscous fluid to the electronic component, wherein the viscous fluid isstirred and put on a belt surface of a belt conveyer, and the viscousfluid put on the belt surface is uniformly flattened by a squeegeeprovided above the belt surface with a delivery operation of the beltconveyor, thereby forming the viscous fluid transfer surface.

[0060] In the viscous fluid transfer method, the viscous fluid isstirred and put on the belt surface of the belt conveyer and isuniformly flattened over the belt surface through the squeegee so thatthe viscous fluid transfer surface can be formed continuously.Consequently, a new viscous fluid transfer surface can always be exposedcontinuously.

[0061] A twenty-second aspect of the invention is directed to anelectronic component mounting apparatus for sucking and holding anelectronic component and mounting the electronic component into apredetermined mounting position, including an electronic componentsupply member for mounting a plurality of electronic components tosupply a desirable one of the electronic components, a sucking nozzlefor removably sucking and holding the electronic component, anattachment head for holding the sucking nozzle to rise and fall freely,a head moving portion for moving the attachment head in a horizontalplane, and the viscous fluid transfer apparatus according to any ofclaims 1 to 15 for uniformly flattening a viscous fluid on a transferunit to form a flat viscous fluid transfer surface, wherein theelectronic component sucked by the electronic component supply member ismoved onto the transfer unit of the viscous fluid transfer apparatus anda terminal portion of the electronic component is immersed in theviscous fluid transfer surface by the up-down operation of theattachment head, thereby transferring the viscous fluid to theelectronic component.

[0062] In the electronic component mounting apparatus, a desirableelectronic component is sucked and held through the sucking nozzle fromthe electronic component supply member mounting a plurality ofelectronic components thereon, and is positioned on the transfer unit ofthe viscous fluid transfer apparatus by moving the attachment headthrough the head moving portion. Then, the attachment head is brought upand down to immerse the terminal portion of the electronic component inthe viscous fluid transfer surface on the transfer unit, therebytransferring the viscous fluid to the electronic component.Consequently, the viscous fluid can be uniformly transferred to theelectronic component and the electronic component to which the viscousfluid is transferred can be mounted in a predetermined position.

[0063] A twenty-third aspect of the invention is directed to theelectronic component mounting apparatus, wherein the attachment headincludes a rubber pad provided in a tip portion of the sucking nozzleand having a sucking surface which can be inclined freely and can beextended freely in a direction of suction, and a sucking attitudecorrecting member provided around the rubber pad in which a tip portionhas a contact face to contact on a rear face of the electronic componentduring the suction of the electronic component.

[0064] In the electronic component mounting apparatus, the attachmenthead includes a rubber pad provided in the tip portion of the suckingnozzle and a sucking attitude correcting member provided around therubber pad. Consequently, when the rubber pad is caused to contact onthe rear face of the electronic component to suck the electroniccomponent, the rubber pad is contracted in a sucking direction so thatthe rear face of the electronic component contacts on the tip portion ofthe sucking attitude correcting member. Consequently, the contact faceof the tip portion of the sucking attitude correcting member is pushedagainst the rear face of the electronic component so that the suckingattitude of the electronic component is corrected. Then, in the case inwhich the sucking nozzle is pushed against the inclined surface with theelectronic component sucked and a part of the electronic component isseparated from the sucking attitude correcting member, the rubber pad isinclined along the inclined surface so that the suction of theelectronic component is maintained and the electronic component is notremoved from the sucking nozzle. Accordingly, the electronic componentcan be always sucked and maintained stably.

[0065] A twenty-fourth aspect of the invention is directed to theelectronic component mounting apparatus, wherein the sucking attitudecorrecting member is constituted by a pair of rod bodies provided onboth sides of the rubber pad.

[0066] In the electronic component mounting apparatus, the suckingattitude correcting member has such a structure that a pair of rodbodies are provided on both sides of the rubber pad. Consequently, thesucking attitude of the electronic component can be corrected with asimple structure.

[0067] A twenty-fifth aspect of the invention is directed to theelectronic component mounting apparatus, wherein the contact face of thesucking attitude correcting member is formed to be inclined from ahorizontal plane.

[0068] In the electronic component mounting apparatus, the contact faceof the sucking attitude correcting member is formed to be inclined fromthe horizontal plane. Consequently, the electronic component can beinclined at an optional angle to be sucked and held into the suckingnozzle. For example, when the electronic component is to be pushedagainst the inclined surface or is to be sucked from the inclinedsurface, the contact face is previously inclined at the inclinationangle so that the sucking state of the electronic component can bemaintained stably.

[0069] A twenty-sixth aspect of the invention is directed to theelectronic component mounting apparatus, further including a multi-headhaving a plurality of attachment heads arranged in parallel, thetransfer unit of the viscous fluid transfer apparatus including a pansurface having a greater width than an attachment head arrangement widthof the multi-head.

[0070] In the electronic component mounting apparatus, the transfer unitof the viscous fluid transfer apparatus includes a pan surface having agreater width than the attachment head arrangement width of themulti-head. Consequently, the electronic component sucked into theattachment head of the multi-head is simultaneously brought up and downby each attachment head so that the viscous fluid can be transferred ata time. Consequently, the efficiency of the transfer of the viscousfluid to the electronic component can be enhanced and a mounting speedcan be increased.

[0071] A twenty-seventh aspect of the invention is directed to theelectronic component mounting apparatus, wherein the transfer unitincludes a pan surface having a greater width than a double of theattachment head arrangement width of the multi-head.

[0072] In the electronic component mounting apparatus, the transfer unitincludes the pan surface having a greater width than a double of theattachment head arrangement width of the multi-head. Consequently, it ispossible to obtain a sufficient space for simultaneously bringing eachattachment head of the multi-head up and down plural times over the sameviscous fluid transfer surface and it is not necessary to form theviscous fluid transfer surface again for each transfer operation.Consequently, the viscous fluid transfer efficiency can be enhanced andthe mounting speed can be increased.

[0073] A twenty-eighth aspect of the invention is directed to anelectronic component mounting method of mounting an electronic componentin a predetermined mounting position, including the steps of sucking anelectronic component by an attachment head having a sucking nozzle,while uniformly flattening a viscous fluid on a transfer unit having aplanar pan surface to form a viscous fluid transfer surface, moving thesucked attachment head of the electronic component to an upper positionof the viscous fluid transfer surface, bringing the sucking nozzle downuntil a terminal portion of the electronic component is immersed in theviscous fluid transfer surface, raising the sucking nozzle aftertransferring the viscous fluid to the electronic component and movingthe attachment head to a predetermined mounting position, and bringingdown the sucking nozzle in the mounting position, thereby mounting theelectronic component.

[0074] In the electronic component mounting method, the electroniccomponent is sucked into the sucking nozzle of the attachment head,while the viscous fluid is uniformly flattened over the transfer unit toform the viscous fluid transfer surface, thereby moving the suckedattachment head of the electronic component to the upper position of theviscous fluid transfer surface. Consequently, the transfer of theviscous fluid is completely prepared. Next, the sucking nozzle isbrought down until the terminal portion of the electronic component isimmersed in the viscous fluid transfer surface so that the viscous fluidis transferred to the terminal portion, and the sucking nozzle is thenraised and the attachment head is moved to the predetermined mountingposition. Consequently, the electronic component to which the viscousfluid is transferred is positioned in the upper part of the mountingposition. The sucking nozzle is brought down, thereby mounting theelectronic component having the terminal portion to which the viscousfluid is transferred.

[0075] A twenty-ninth aspect of the invention is directed to theelectronic component mounting method, wherein the sucking nozzles of amulti-head having a plurality of attachment heads arranged in parallelare controlled to be brought up and down at the same time.

[0076] In the electronic component mounting method, each sucking nozzleof the multi-head having a plurality of attachment heads arranged inparallel is controlled to carry out the up-down operation at the sametime. For example, consequently, in the case in which the same kind ofelectronic components are sucked into each sucking nozzle, the viscousfluid can be transferred at the same time so that the transferefficiency can be enhanced and the mounting speed can be increased.

[0077] A thirtieth aspect of the invention is directed to the electroniccomponent mounting method, wherein a height of the viscous fluidtransfer surface of the transfer unit is detected before the viscousfluid is transferred to the electronic component, and an amount of fallof the sucking nozzle of the attachment head is set according to theheight thus detected.

[0078] In the electronic component mounting method, the height of theviscous fluid transfer surface of the transfer unit is detected beforethe viscous fluid is transferred to the electronic component so that theamount of fall of the sucking nozzle required before the electroniccomponent comes in contact with the viscous fluid transfer surface isobtained with high precision. Accordingly, the height of the electroniccomponent from the viscous fluid transfer surface can be set with highprecision and the viscous fluid can be immersed in the electroniccomponent in a desirable thickness.

[0079] A thirty-first aspect of the invention is directed to theelectronic component mounting method, wherein the viscous fluid transfersurface having a predetermined thickness is formed on the transfer unitand the terminal portion of the electronic component is pushed tocontact on the pan surface of the transfer unit, thereby transferringthe viscous fluid having the predetermined thickness to the electroniccomponent.

[0080] In the electronic component mounting method, the terminal portionof the electronic component is pushed against the viscous fluid transfersurface formed on the transfer unit in a predetermined thickness tocontact on the pan surface. Consequently, the viscous fluid for theheight of the viscous fluid transfer surface is transferred from the pansurface to the terminal portion of the electronic component.Accordingly, when the viscous fluid having a thickness suitable for theelectronic component is formed on the transfer unit, the viscous fluidcan be easily transferred in a proper thickness to the electroniccomponent by a simple push operation without setting the amount ofmovement of the sucking nozzle with high precision.

[0081] A thirty-second aspect of the invention is directed to theelectronic component mounting method, wherein the electronic componentto which the viscous fluid is transferred is stacked and mounted on arear face opposite to a mounting surface side of the electroniccomponent which has already been mounted on a circuit board.

[0082] In the electronic component mounting method, the electroniccomponent to which the viscous fluid is transferred is stacked andmounted on the rear face opposite to the mounting surface side of theelectronic component which has already been mounted on a circuit board.Consequently, the electronic component can be stacked and mounted in thesame space in the plane of the circuit board so that the mountingdensity of the circuit board can be enhanced.

[0083] A thirty-third aspect of the invention is directed to theelectronic component mounting method, wherein a reference mark foralignment provided on the rear face of the mounted electronic componentis detected and a mounting position of the electronic component to bestacked and mounted on the rear face is corrected by setting thedetected reference mark as a reference.

[0084] In the electronic component mounting method, the reference markfor alignment provided on the rear face of the mounted electroniccomponent is detected and the mounting position or mounting angle of theelectronic component is detected. By setting the detected reference markas a reference to correct the mounting position of the electroniccomponent to be mounted on the rear face, the electronic component canbe mounted on the rear face of the mounted electronic component bycanceling a shift in the mounting position. Accordingly, the electroniccomponent to be mounted on the rear face of the mounted electroniccomponent can be aligned and stacked with high precision for the mountedelectronic component.

[0085] A thirty-fourth aspect of the invention is directed to asemiconductor device having a plurality of solder balls arranged asconnecting terminals on a mounting surface side, wherein a land forterminal connection is provided in a position corresponding to theconnecting terminal of the semiconductor device on a rear face oppositeto the mounting surface side.

[0086] In the semiconductor device, the land for terminal connection isprovided in the position corresponding to the connecting terminal of thesemiconductor device on the rear face of the semiconductor device.Consequently, the land of the semiconductor device on the lower stageside and the connecting terminal of the semiconductor device on theupper stage side are connected to each other when the semiconductordevice is stacked. Thus, the semiconductor device can be simplified andcan be constituted as a stacked structure.

[0087] A thirty-fifth aspect of the invention is directed to thesemiconductor device, wherein the connecting terminal of thesemiconductor device has a solder fixed to a heat-resistant pin.

[0088] In the semiconductor device, even if the length of the pin is notequal, the solder absorbs the shortage of the length thereof and isreliably connected to the land. By setting the lower end of the pin tobe a plane, moreover, the attitude of the electronic component can bestably fixed without an inclination from the circuit board surface. Evenif the solder is exposed to a high temperature in a reflow processcarried out again, furthermore, it is maintained to stick around the pinby a surface tension. Therefore, electrodes can be prevented from beingshort-circuited.

[0089] A thirty-sixth aspect of the invention is directed to thesemiconductor device, wherein a reference mark for alignment is providedon the rear face opposite to the mounting surface side.

[0090] In the semiconductor device, when the semiconductor device is tobe stacked and mounted, the connecting terminal of the semiconductordevice on the upper stage side can be aligned with the land of thesemiconductor device on the lower stage side with high precision. Evenif the semiconductor device on the lower stage side is shifted from apredetermined position, the amount of the shift can be cancelled and thesemiconductor device can be stacked.

BRIEF DESCRIPTION OF THE DRAWINGS

[0091]FIG. 1 is a perspective view showing an electronic componentmounting apparatus including a viscous fluid transfer apparatusaccording to the invention.

[0092]FIG. 2 is an enlarged perspective view showing the transfer headof the electronic component mounting apparatus.

[0093]FIG. 3 is a schematic plan view for illustrating the operation ofthe electronic component mounting apparatus.

[0094] FIGS. 4(a), (b), and (c) are views showing a three-dimensionalmounting method for mounting an electronic component in a multi-stage.

[0095]FIG. 5 is a perspective view showing the schematic structure of asolder cream transfer apparatus attached to the electronic componentmounting apparatus and serving to transfer a solder cream to theelectronic component.

[0096]FIG. 6 is a side view showing the solder cream transfer apparatus,a part of which is taken away.

[0097]FIG. 7 is an enlarged view showing the positional relationshipbetween an arm for controlling the rocking motion of a rocking arm, astirring squeegee and a leveling squeegee, and an arm stopper.

[0098]FIG. 8 is a view seen in the direction of an arrow A of FIG. 7.

[0099]FIG. 9 is a top view showing a squeegee unit.

[0100]FIG. 10 is a side view showing the solder cream transfer apparatusseen from the side of attachment to the electronic component mountingapparatus.

[0101]FIG. 11 is a side view showing the squeegee unit.

[0102]FIG. 12(a) is an exploded view showing the support structure of aburied pin seen in a direction of B in FIG. 10 and FIG. 12(b) is a viewseen in the direction of B in an assembly state thereof.

[0103]FIG. 13(a) is an exploded view showing the support structure of anengagement portion seen in a section taken along C-C in FIG. 10 and FIG.13(b) is a sectional view taken along C-C in an assembly state thereof.

[0104] FIGS. 14(a) and (b) are views in which the lengths of thestirring squeegee and the leveling squeegee are compared with eachother.

[0105] FIGS. 15(a) and (b) are views showing the shape of the levelingsqueegee, FIG. 15(a) being a front view and FIG. 15(b) being a sectionalview taken along D-D.

[0106]FIG. 16 is a view showing the state of scrape of the levelingsqueegee.

[0107] FIGS. 17(a) and (b) are views showing the shape of the stirringsqueegee, FIG. 17(a) being a front view and FIG. 17(b) being a bottomview.

[0108]FIG. 18 is a sectional view taken along E-E in FIG. 17.

[0109]FIG. 19 is an enlarged perspective view showing both ends on thesolder cream press side of the stirring squeegee.

[0110]FIG. 20 is a view illustrating the flow of a solder cream with asqueegee movement.

[0111] FIGS. 21(a), (b), and (c) are views illustrating the operation ofthe solder cream transfer apparatus on a stepwise basis.

[0112] FIGS. 22(a), (b), and (c) are views illustrating the operation ofthe solder cream transfer apparatus on a stepwise basis.

[0113] FIGS. 23(a), (b), (c) and (d) are views illustrating, on astepwise basis, a state in which the transfer surface of the soldercream is formed by using the solder cream transfer apparatus.

[0114] FIGS. 24(a) and (b) are views showing the structure of a suckingnozzle, FIG. 24(a) being a front view and FIG. 24(b) being a side view,a part of which is taken away.

[0115] FIGS. 25(a), (b), and (c) are views showing a state in which thesolder cream is transferred to the electronic component over the pansurface of a transfer unit inclined from a horizontal plane.

[0116] FIGS. 26(a), (b), and (c) are views showing a state in which theelectronic component mounted on the surface inclined from the horizontalplane is sucked.

[0117]FIG. 27 is a view showing a state in which a space between the tipportions of a sucking component correcting member is enlarged.

[0118] FIGS. 28(a), (b), and (c) are views showing a state in which thesolder cream on the pan surface of the transfer unit of the solder creamtransfer apparatus is transferred to the electronic component by usingthe sucking nozzle.

[0119]FIG. 29 is an enlarged view showing a solder ball obtained afterthe transfer of the solder cream.

[0120]FIG. 30 is a view showing the push-in depth of the solder ball.

[0121] FIGS. 31(a) and (b) are views showing a state in which a transferoperation is carried out over the same solder cream transfer surfaceplural times.

[0122] FIGS. 32(a) and (b) is a view showing another state in which atransfer operation is carried out over the same solder cream transfersurface plural times.

[0123]FIG. 33 is a view showing a state in which the transfer operationshown in FIG. 31 and the transfer operation shown in FIG. 32 arecombined to carry out a transfer operation.

[0124] FIGS. 34(a), (b), and (c) are views showing the appearance of theelectronic component to be mounted three-dimensionally, FIG. 34(a) beinga plan view, FIG. 34(b) being a side view and FIG. 34(c) being a bottomview.

[0125] FIGS. 35(a), (b), (c), (d), (e), (f), (g), and (h) are viewsillustrating a procedure for a three-dimensional mounting method.

[0126]FIG. 36 is a view showing an example in which the solder ball ofthe electronic component is constituted by a combination of a pin andthe solder ball.

[0127]FIG. 37 is a view showing the state of a connecting terminalportion which is obtained after a reflow process.

[0128] FIGS. 38(a), (b), (c), and (d) are views illustrating a method ofaligning the electronic component in the three-dimensional mountingmethod.

[0129]FIG. 39 is an enlarged view showing the tip potion of a levelingsqueegee according to a second embodiment.

[0130] FIGS. 40(a) and (b) are views showing the shape of the levelingsqueegee and the state of squeegee movement according to a variant ofthe second embodiment.

[0131]FIG. 41 is a side view showing the structure of attachment of apressure generating member according to a third embodiment.

[0132] FIGS. 42(a) and (b) are views showing the shape of a stirringsqueegee according to a fourth embodiment.

[0133]FIG. 43 is a sectional view taken along F-F in FIGS. 42(a) and(b).

[0134] FIGS. 44(a), (b), and (c) are views illustrating a state in whicha solder cream transfer surface is formed on a transfer unit by usingthe stirring squeegee.

[0135] FIGS. 45(a) and (b) are views showing the shape of a stirringsqueegee according to a fifth embodiment.

[0136]FIG. 46 is a sectional view taken along G-G in FIGS. 45(a) and(b).

[0137]FIG. 47 is a view showing the state of solder cream transferaccording to a sixth embodiment.

[0138]FIG. 48 is a view showing the section of a transfer unit and aleveling squeegee to slidably come in contact with the transfer unitaccording to a seventh embodiment.

[0139]FIG. 49 is a view showing a state in which a solder cream istransferred to an electronic component sucked by a sucking nozzle over aformed solder cream transfer surface.

[0140]FIG. 50 is a view showing a structure in which a stepped portionis provided in a higher position than the radius of a solder ball fromthe pan surface of the transfer unit.

[0141]FIG. 51 is a view showing a structure in which a stepped portionis provided in a leveling squeegee according to a variant of the seventhembodiment.

[0142]FIG. 52 is a view showing a state obtained during the transfer ofa solder cream.

[0143]FIG. 53 is a plan view showing the transfer unit of a solder creamtransfer apparatus according to an eighth embodiment.

[0144]FIG. 54 is a view showing the schematic structure of a soldercream transfer apparatus according to a ninth embodiment.

[0145]FIG. 55 is a sectional view taken along H-H in FIG. 54.

[0146]FIG. 56 is a partial sectional view taken along I-I in FIG. 54.

[0147] FIGS. 57(a), (b), and (c) are views showing a procedure fortransferring a solder cream to an electronic component by the soldercream transfer apparatus on a stepwise basis.

[0148] FIGS. 58(a) and (b) are views showing a double-sided mountingstate in the package technique of a conventional electronic component.

[0149] FIGS. 59(a) and (b) are views showing a device for forming thetransfer surface of a conventional flux.

[0150] FIGS. 60(a) and (b) is a view showing the device for forming thetransfer surface of the conventional flux.

[0151]FIG. 61 is a view showing a state in which a solder cream istransmitted toward the upper part of a squeegee with a viscositythereof.

[0152]FIG. 62 is a view showing a state in which the solder cream istransferred to an electronic component by using a transfer unit havingan inclined pan surface.

[0153] FIGS. 63(a) and (b) are views showing a state in which a push-indepth cannot be controlled when a rubber pad is to be attached to thetip portion of a sucking nozzle and the electronic component is to bepushed into the surface of the solder cream.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0154] Preferred embodiments of a viscous fluid transfer apparatus, anelectronic component mounting apparatus and a semiconductor deviceaccording to the invention will be described below in detail withreference to the drawings.

[0155]FIG. 1 is a perspective view showing an electronic componentmounting apparatus including a viscous fluid transfer apparatus(hereinafter referred to as a solder cream transfer apparatus using asolder cream as a viscous fluid) according to the invention. FIG. 2 isan enlarged perspective view showing the transfer head of the electroniccomponent mounting apparatus. FIG. 3 is a schematic plan view forillustrating the operation of the electronic component mountingapparatus.

[0156] First of all, the structure of an electronic component mountingapparatus 100 according to the invention will be described.

[0157] As shown in FIG. 1, a guide rail 114 for mounting a circuit board10 is provided on the center of the upper surface of a base 110 of theelectronic component mounting apparatus 100, and the circuit board 10 isdelivered from a loader portion 116 on one of end sides to an electroniccomponent mounting position 118, and furthermore, from the mountingposition 118 to an unloader portion 120 on the other end side throughthe delivery belt of the guide rail 114.

[0158] Both side portions of the upper surface of the upper base 110provided above the circuit board 10 are provided with Y tables 122 and124 respectively, and an X table 126 is provided between these two Ytables 122 and 124. Moreover, a transfer head 128 is attached to the Xtable 126 so that the transfer head 128 can be moved in an X-Y plane.

[0159] The transfer head 128 mounted on a head moving portion includingthe X table 126 and the Y tables 122 and 124 and movable over the X-Yplane (horizontal plane) is constituted such that a desirable electroniccomponent is sucked through a sucking nozzle 134 from a parts feeder 130for feeding an electronic component such as a resistance chip or a chipcapacitor or a parts tray 132 for feeding a comparatively large-sizedelectronic component such as an IC, for example, an SOP, a GFP or a BGAor a connector and the sucking attitude of the electronic component isdetected from a recognizing device 136 and the electronic component canbe then attached to the predetermined position of the circuit board 10.Moreover, the transfer head 128 is provided with a recognizing camera135 such as a CCD camera for detecting the position of the circuit boardand a length measuring sensor, which is not shown (the details will bedescribed below).

[0160] Such an electronic component mounting operation is controlledbased on a preset mounting program by a controller (main controller)which is not shown. Data can be input to the controller through anoperation panel 152.

[0161] The mounting program serves to carry out a recombination processof a mounting order over NC information input to the electroniccomponent mounting apparatus 100 and having information about anelectronic component to be mounted and to convert the recombined datathus created into an instruction configuration for driving the headmoving portion or the nozzle of the transfer head. The mounting programis created through the input of an operator by using the NC informationrecording information about the mounting position of each electroniccomponent and component data registering information about the electrodeshape of each electronic component. The controller executes the mountingprogram thus created so that the electronic component is mounted ontothe circuit board.

[0162] A large number of parts feeders 130 are arranged on both ends ofthe guide rail 114 and a tape-shaped component roll accommodating anelectronic component such as a resistance chip or a chip capacitor isattached to each of the parts feeders 130.

[0163] Moreover, the parts tray 132 can mount two trays 132 a in totalwhich are elongated in a direction orthogonal to the guide rail 114, andeach of the trays 132 a is so constituted as to slide toward the guiderail 114 side corresponding to the number of components to be fed,thereby maintaining a component take-out position in a Y direction to bea constant position. The electronic component such as a QFP or a BGA ismounted on the ray 132 a.

[0164] The recognizing device 136 is provided in the side portion of theguide rail 114 and includes an attitude recognizing camera for detectingthe two-dimensional shift (suction attitude) of an electronic componentsucked into the sucking nozzle 134 and for carrying out correction onthe transfer head 128 side to cancel the shift. The attitude recognizingcamera is provided in a bottom portion on the inside of the recognizingdevice 136 and the internal surface of the housing of the recognizingdevice 136 provided around the attitude recognizing camera is providedwith a plurality of multi-stage light emitting elements such as a lightemitting diode LED for illuminating the electronic component sucked intothe sucking nozzle 134. Consequently, light can be irradiated on themounting surface of the electronic component at a desirable angle and animage can be picked up at a proper illumination angle according to thetype of the component. The pick-up data thus obtained are subjected to arecognition process by the controller, and the central position or theelectrode position of the sucked electronic component is recognized andis used for correction data on a mounting position and a rotation angle.

[0165] The transfer head 128 is constituted as a multiple multi-headhaving a plurality of (four in the embodiment) attachment heads (a firstattachment head 138 a, a second attachment head 138 b, a thirdattachment head 138 c and a fourth attachment head 138 d) coupled in atransverse direction. The four attachment heads 138 a, 138 b, 138 c and138 d have the same structure and include the sucking nozzle 134, anactuator 140, a motor 142, a timing belt 144 and a pulley 146. Theactuator 140 causes the sucking nozzle 134 to carry out a verticaloperation. And the three members, that are the motor 142, the timingbell 144, and the pulley 146, cause the sucking nozzle 134 to carry outa θ rotation.

[0166] The sucking nozzle 134 of each attachment head is exchangeableand other sucking nozzles, that are substitutive nozzles, are previouslyaccommodated in a nozzle stocker 148 provided on the base 110 of theelectronic component mounting apparatus 100. Examples of the suckingnozzle 134 include an S size nozzle sucking a very small chip componenthaving a size of approximately 1.0×0.5 mm and an M size nozzle sucking aQFP of 18 mm square which are selectively used depending on the type ofthe electronic component to be attached.

[0167] Moreover, the attachment heads 138 a, 138 b, 138 c and 138 dbring down the sucking nozzle 134 from the X-Y plane in a verticaldirection (a Z direction) when the electronic component is to be suckedfrom the parts feeder 130 or the parts tray 132 through the suckingnozzle 134, when the electronic component is to be attached to thepredetermined position of the circuit board 10 and when the solder creamis to be transferred from the transfer unit 210. Furthermore, thesucking nozzle is properly exchanged to carry out an attachmentoperation depending on the type of the electronic component.

[0168] The electronic component mounting apparatus 100 according to theinvention comprises a solder cream transfer apparatus 200 fortransferring the solder cream to the connecting terminal of theelectronic component such as a BGA, and the solder cream transferapparatus 200 is attached to a parts feeder fixing table 154 and thesolder cream is put on the transfer unit 210.

[0169] In this specification, the solder cream implies a paste-shapedsolder mixing a solder powder with a flux having a high viscosity.

[0170] Next, the schematic operation of the electronic componentmounting apparatus 100 having the above-mentioned structure will bedescribed.

[0171] As shown in FIG. 3, when the circuit board 10 delivered from theloader portion 116 of the guide rail 114 is delivered to thepredetermined mounting position 118, the transfer head 128 is moved inthe X-Y plane by the head moving portion so that a desirable electroniccomponent is sucked from the parts feeder 130 or the parts tray 132based on a mounting program. In the drawing, a state in which theelectronic component is sucked from the parts feeder 130 is shown. Then,the transfer head 128 is moved over the attitude recognizing camera ofthe recognizing device 136. The recognizing device 136 recognizes thesucking attitude of the electronic component based on componentrecognition data to carry out an operation for correcting a suckingattitude.

[0172] The correcting operation is carried out by causing the headmoving portion to have a shift in X and Y directions as an offset orrotating the sucking nozzle 134 with a shift for a rotation componentthrough a motor 142. After the correcting operation is carried out, thesucked electronic component is attached to the predetermined position ofthe circuit board 10.

[0173] By repeating the suction of the electronic component and theoperation for attachment to the circuit board 10, the electroniccomponent is completely mounted on the circuit board 10. When themounting is completed, the circuit board 10 is delivered from themounting position 118 to the unloader portion 120, while a new circuitboard is delivered into the loader portion 116 so that the operationdescribed above is repeated.

[0174] While the electronic component is thus mounted on the circuitboard 10, the electronic component mounting apparatus according to theinvention can carry out a three-dimensional mounting method of mountinga plurality of electronic components such as ICs (semiconductor devices)in a multi-stage as shown in FIGS. 4(a), (b), and (c) in order tofurther enhance a mounting density. In the three-dimensional mountingmethod, first of all, the solder cream 30 is mask printed on the land 24formed in the circuit board 10. Then, the electronic component (a BGA asan example of the drawing) 20 having the land 25 formed on a rear faceopposite to the mounting surface side is aligned and mounted on thesolder cream 30 transferred onto each land 24 such that the terminalportion (solder ball 26) on the mounting surface side and the land 24 onthe circuit board 10 are connected to each other (FIG. 4(a)).Furthermore, the electronic component 22 having the solder cream 30 in apredetermined amount transferred to the solder ball 26 is aligned andmounted such that the solder ball of the electronic component 22 isconnected to the rear face side land 25 of the mounted electroniccomponent 20 (FIG. 4 (b)). Consequently, it is possible to obtain athree-dimensional stack structure in which the electronic components 20and 22 are mounted onto the same space on the circuit board 10 (FIG.4(c)). Thus, the mounting density can be enhanced.

[0175] The print of the solder cream 30 onto the land 24 on the circuitboard 10 can also be omitted by transferring the solder cream 30 ontothe solder ball 26 side of the electronic component 20 and then carryingout the mounting.

[0176] Next, the structure of each portion of the solder cream transferapparatus 200 for implementing the three-dimensional mounting methodwill be sequentially described in detail.

[0177]FIG. 5 is a perspective view showing the schematic structure ofthe solder cream transfer apparatus 200 attached to the electroniccomponent mounting apparatus 100 and serving to transfer a solder creamto an electronic component and FIG. 6 is a side view showing the soldercream transfer apparatus 200, a part of which is taken away.

[0178] As shown in FIGS. 5 and 6, the solder cream transfer apparatus200 includes a housing 214 and a transfer unit 218. In the housing 214,an engagement tool 212 is provided on the attachment direction side toan electronic component mounting apparatus 100. The engagement tool 212is to be attached to a parts feeder fixing table 154 of the electroniccomponent mounting apparatus 100. Moreover, a transfer transfer unit 210is accommodated in the housing 214, The transfer unit 218 includes thetransfer unit 210 and a squeegee unit 216.

[0179] The transfer unit 218 includes the transfer unit 210 exposed tothe upper surface side of the solder cream transfer apparatus 200 andhaving a planar pan surface 220 forming the transfer surface of thesolder cream, a squeegee unit 216 provided slidably in contact with theupper part of the pan surface 220 of the transfer unit 210 and servingto flatly put a solder cream on the transfer unit 210 by alternatelyusing two squeegees of a stirring squeegee 222 and a leveling squeegee224, and a transfer unit moving mechanism (not shown) for reciprocatingthe transfer unit 210 in the Y direction of the drawing such that eachof the squeegees 222 and 224 is relatively moved over the pan surface220, and furthermore, a rocking arm 226 having one end side 226 a fixedto the attachment side of the stirring squeegee 222 and the levelingsqueegee 224 and the other end side 226 b slidably supported and havingrocking control arms 226 c and 226 d for controlling a rocking angle, ahorizontal driving mechanism 228 for rocking the rocking arm 226 byreciprocating the other end side 226 b of the rocking arm 226 in the Ydirection, and arm stoppers 230 and 232 contacting on the rockingcontrol arms 226 c and 226 d of the rocking arm 226 to control therocking angle of the rocking arm 226.

[0180] The squeegee unit forms a flat solder cream transfer surface andstirs a solder cream which can easily become dry and hard, therebymaintaining a uniform state in which the solder cream transfer surfacealways has a proper viscosity.

[0181]FIG. 7 shows the enlarged positional relationship between therocking control arms 226 c and 226 d of the rocking arm 226, thestirring squeegee 222 and the leveling squeegee 224, and the armstoppers 230 and 232.

[0182] As shown in FIG. 7, in the rocking arm 226, two states of the useof the stirring squeegee 222 shown in a solid line of the drawing andthe use of the leveling squeegee 224 shown in a two-dotted line areselectively set with the end 226 a on the squeegee unit 216 side of therocking arm 226 to be a rocking center. More specifically, the rockingcontrol arm 226 d of the rocking arm 226 contacts on the tip portion ofa screw 234 of the arm stopper 232 in the state of the use of thestirring squeegee 222, and the rocking control arm 226 c of the rockingarm 226 contacts on the tip portion of the screw 234 of the arm stopper230 to control a rocking angle in the state of the use of the levelingsqueegee 224. The rocking arm 226 is provided on either side of thetransfer unit 210, and each of the squeegees 222 and 224 is rockedaccording to the movement of the rocking arm 226 on the other side.

[0183] The arm stoppers 230 and 232 have an arrow 234 a provided on thepan portion of the screw 234 through marking as shown in a view of FIG.8 seen in the direction of an arrow A of FIG. 7, while a cylindricalring 236 is provided around the screw 234 to be fastened with a fixingscrew 238. The upper end face of the cylindrical ring 236 is providedwith a graduation 240 corresponding to the arrow 234 a and a part of aside surface is provided with a rotation regulating lever 242. Theheight of the screw 234 is set such that the stirring squeegee 222 andthe leveling squeegee 224 are fixed to the pan surface 220 of thetransfer unit 210 with predetermined clearances respectively.

[0184] At this time, the height is regulated as follows. The rotationregulating lever 242 is rotated such that any graduation 240 of thecylindrical ring 23 is coincident with the arrow 234 a of the screw 234with the fixing screw 238 loosened, and the fixing screw 238 is loosenedto fix the cylindrical ring 236 in a position where the coincidence iscarried out. Then, the screw 234 is rotated by referring to thegraduation 240 through a tool such as a screw driver so that the heightcan be controlled with high precision by a simple structure. In theembodiment, one graduation is set to 15 degrees. When the screw 234 isrotated clockwise by one graduation, the clearances between thesqueegees 222 and 224 and the pan surface 220 are set to be enlarged by0.005 mm.

[0185] Next, the squeegee unit 216 will be described.

[0186] In the solder cream transfer apparatus 200, a cleaning work isrequired for the squeegee unit 216 and portions to be cleaned arecollectively constituted removably, thereby enhancing a maintenanceproperty. Moreover, the reproducibility of a position where each memberis to be provided for recombination can be implemented with very highprecision.

[0187]FIG. 9 is a top view showing the squeegee unit 216, FIG. 10 is aside view showing the solder cream transfer apparatus 200 seen from theattachment side to the electronic component mounting apparatus 100, andFIG. 11 is a side view showing the squeegee unit.

[0188] As shown in FIGS. 9, 10, and 11, the squeegee unit 216 is mainlyconstituted by the stirring squeegee 222, the leveling squeegee 224, anda rod-shaped squeegee fixing member 250 fixed in parallel with thesqueegees 222 and 224 separated from each other and having both endssupported on the housing 214. The squeegees 222 and 224 are formed tohave almost planar shapes and are interposed between the fixed plates252 and 254 and the squeegee fixing member 250 and are fixed with screws256 and 258, respectively. The squeegee fixing member 250 has a squeegeeattachment surface previously cut to have a predetermined squeegeeinclination angle when the squeegee is attached to the squeegeeattachment surface.

[0189] Moreover, a fitting hole 260 is formed in an end face on one ofthe end sides of the squeegee fixing member 250 and an embedded pin 262is inserted in the fitting hole 260. The head portion of the embeddedpin 262 is cylindrically formed to have a larger diameter than thediameter of the fitting hole. As shown in an exploded view of FIG. 12(a)showing the support structure of the embedded pin 262 seen in adirection of B of FIG. 10 and a view of FIG. 12(b) showing an assemblystate in the direction of B, is the cylindrical head portion of theembedded pin 262 is interposed between a lower V block 266 fixed to thehousing 214 and an upper V block 268. Moreover, a screw 270 is attachedto the lower V block 266 through the upper V block 268 so that the headportion of the embedded pin 262 is positioned and fixed with highprecision between the upper V block 268 and the lower V block 266.

[0190] On the other hand, the other end side of the squeegee fixingmember 250 is provided with an engagement portion 274 having an upperend side protruded like a plate in an axial direction, and a key groove276 is formed in the axial direction on the lower surface side of theengagement portion 274. FIG. 13(a) is an exploded view showing thesupport structure of the engagement portion 274 seen in a C-C section ofFIG. 10 and FIG. 13(b) is a sectional view taken along C-C in anassembly state thereof. The engagement portion 274 has a projection 278to be engaged with the key groove 276 and is fixed with a screw 282 to areceiving table 280 fastened to the housing 214 side so that the keygroove 276 of the engagement portion 274 and the projection 278 of thereceiving table 280 are fitted and positioned with high precision.

[0191] According to the support structure of the squeegee fixing member250, one of end sides is supported on the lower V block 266 and theupper V block 268 and the other end side is supported by the fitting ofthe key groove 276 and the projection 278. Consequently, the squeegeefixing member 216 itself can be prevented from being twisted and aremoving method having high reproducibility of an attachment positionand high precision can be implemented.

[0192] Next, description will be given to the stirring squeegee 222 andthe leveling squeegee 224 which are to be attached to the squeegee unit216.

[0193] FIGS. 14(a) and (b) are views showing a comparison of the lengthsof the stirring squeegee 222 and the leveling squeegee 224. A length L₁of the stirring squeegee 222 may be equal to a length L₂ of the levelingsqueegee 224 as shown in FIG. 14(a). In order to reliably prevent thesolder cream from overlapping, however, it is desirable that the lengthL₁ of the leveling squeegee 224 should be set to be greater than thelength (a scrape-off width) L₂ of the stirring squeegee as shown in FIG.14 (b). These squeegees 222 and 224 are formed like plates and a hardrubber such as an urethane rubber is used for a material thereof.

[0194] First of all, the leveling squeegee 224 will be described.

[0195] FIGS. 15(a) and (b) are views showing the shape of the levelingsqueegee 224, FIG. 15(a) being a front view and FIG. 15(b) being asectional view taken along D-D. The plate-shaped leveling squeegee 224has a fixing hole 224 a to the squeegee fixing member 250 provided onone of the sides of a long side thereof, and a concave sectional curvedportion 224 b and a convex sectional curved potion 224 c aresequentially formed in the press portion of the solder cream on thelower end of the drawing from the front part in the direction ofprogress of the squeegee.

[0196] In the leveling squeegee 224, as shown in the state of scrape-offin FIG. 16, the solder cream is pressurized and extended by the convexsectional curved portion 224 c to form a layer having a uniform soldercream thickness, and an excessive solder cream is rolled along thecurved surface of the concave sectional curved portion 224 b in thedirection of progress of the squeegee and is stirred and returned to theprogress side of the squeegee. Consequently, the solder cream thusstirred is always put with a uniform thickness.

[0197] Next, the stirring squeegee 222 will be described.

[0198] FIGS. 17(a) and (b) are views showing the shape of the stirringsqueegee 222, FIG. 17(a) being a front view and FIG. 17(b) being abottom view. FIG. 18 is a sectional view taken along E-E in FIGS. 17(a),17(b) and 19 is an enlarged perspective view showing both ends on thesolder cream press side of the stirring squeegee 222. Portions shown ina slant line in FIGS. 17(b) and 19 show the lowermost surface of thestirring squeegee 222.

[0199] As shown in FIGS. 17(a), 17(b) and 18, the plate-shaped stirringsqueegee 222 is provided with the fixing hole 222 a to the squeegeefixing member 250 on one of the sides of a long side thereof, and aprotrusion 310 having a taper face 310 a for scraping the solder creamtoward the central side in the longitudinal direction of the squeegeewith the movement of the squeegee is formed on the pan surface side tobe the press side of the solder cream on the lower end shown in FIG.17(a) on both ends in the longitudinal direction. The taper face 310 aof the protrusion 310 is inclined in such a direction that an openinglength L₃ on the outlet side is set to be smaller than the squeegeelength L₁ on the solder cream inlet side of the stirring squeegee 222 toreduce the passage for the solder cream. Moreover, the stirring squeegee222 is used in a forward inclination state in the direction of progressby a predetermined angle θ_(s). Therefore, the protrusion 310 of thesqueegee 222 is cut at the angle of θ_(s) as shown in FIG. 18.Accordingly, the protrusion 310 of the stirring squeegee 222 has alongitudinal section taking a triangular shape and has such a shape thata triangle pole is obliquely cut at the angle of θ_(s) as in theenlarged protrusion 310 shown in FIG. 19.

[0200] By setting the stirring squeegee 222 to have the shape describedabove, the flow of the solder cream caused by the movement of thesqueegee is stirred and scraped toward the central side in thelongitudinal direction of the squeegee as shown in FIG. 20. Morespecifically, the solder cream introduced from an opening on the soldercream inlet side of the stirring squeegee 222 is scraped toward theinside along the taper face 310 a of the protrusion 310 and is putwithout overflowing from ends in the lateral direction of the stirringsqueegee 222. Consequently, it is possible to prevent the solder creamfrom overflowing from the pan surface of the transfer unit with a simplestructure.

[0201] Description will be given to a procedure for forming a soldercream transfer surface by the solder cream transfer apparatus 200 havingthe structure of the main part described above. FIGS. 21(a), 21(b) and22 show the operation of the solder cream transfer apparatus 200 on astepwise basis.

[0202] First of all, in an initial state shown in FIG. 21(a), the rod ofthe horizontal driving mechanism 228 is contracted with a reduction inthe protrusion of the tip portion of the screw 234 of the arm stopper230 and the tip of the leveling squeegee 224 is pushed against the pansurface 220 of the transfer unit 210 over the whole width. By settingthe push position to be a reference position, the degree of parallelismof the pan surface 220 and the leveling squeegee 224 is enhanced. Inthis state, the screw 234 of the arm stopper 230 is protruded downwarduntil the tip portion of the screw contacts on the rocking control arm226 c of the rocking arm 226. After the graduation 240 of thecylindrical ring 236 shown in FIG. 8 is coincident with the arrow 234 aof the screw 234 in a position where the screw 234 contacts on therocking control arm 226 c, the height of the leveling squeegee 224 isset by the rotation of the screw 234 such that the clearance between theleveling squeegee 224 and the pan surface 220 has a desirable soldercream thickness. At this time, the pitch of the screw 234 accuratelydetermines the amount of change in the height of one graduation 240. Byregulating the rotating position of the screw 234 (arrow 234 a) usingthe graduation 240 of the cylindrical ring 236, the clearance can be setwith high precision. Moreover, the tip of the squeegee can be preventedfrom being excessively pushed against the pan surface 220 through thearm stopper 230.

[0203] As shown in FIG. 21(b), next, the rod of the horizontal drivingmechanism 228 is extended to rock the rocking arm 226 around the endside 226 a on the squeegee unit 216 side. At this time, the degree ofparallelism of the stirring squeegee 222 and the pan surface 220 isenhanced in the same manner as described above, thereby setting theclearance between the stirring squeegee 222 and the pan surface 220 withhigh precision through the arm stopper 232.

[0204] After the clearance between each squeegee and the pan surface 220is regulated, the transfer unit 210 is moved from the state shown inFIG. 21(b) in the right direction of the drawing through a transfer unitmoving mechanism which is not shown as illustrated in FIG. 21 (c).Consequently, the solder cream having a thickness corresponding to theclearance set between the stirring squeegee 222 and the pan surface 220is stirred and put on the pan surface 220.

[0205] As shown in FIG. 22(a), next, the rod of the horizontal drivingmechanism 228 is contracted to rock the rocking arm 226 up to such aposition that the rocking control arm 226 c contacts on the tip portionof the screw 234 of the arm stopper 230 around the end 226 a of therocking arm 226. Consequently, the stirring squeegee 222 is separatedfrom the pan surface 220 and the leveling squeegee 224 is set to a spaceformed together with the pan surface 220 regulated previously.

[0206] The transfer unit 210 is moved from the state shown in FIG. 22(a)in the left direction of the drawing through the transfer unit movingmechanism as shown in FIG. 22(b). Consequently, the solder cream isuniformly put with a predetermined thickness over the pan surface 220 ofthe transfer unit 210 and the solder cream transfer surface iscompletely formed. As shown in FIG. 22(c), the sucking nozzle 134sucking a predetermined electronic component is pushed against thesolder cream transfer surface so that the solder cream is transferred tothe electronic component.

[0207] According to the procedure for forming the solder cream transfersurface of the solder cream transfer apparatus 200, moreover, the soldercream on the transfer unit 210 of the solder cream transfer apparatus200 is put in such a configuration as to be shown in FIGS. 23(a), (b),(c), and (d). FIGS. 23(a), (b), (c) and (d) illustrate, on a stepwisebasis, a state in which the transfer surface of the solder cream isformed by using the solder cream transfer apparatus 200 according to theembodiment.

[0208] First of all, as shown in FIG. 23(a), the solder cream 30 isalmost uniformly leveled and provided on the pan surface 220 of thetransfer unit 210. As shown in FIG. 23(b), then, the stirring squeegee222 is moved toward the left side in the drawing, thereby stirring andputting the solder cream 30 on the pan surface 220. As shown in FIG.23(c), furthermore, when the leveling squeegee 224 is moved to the rightside in the drawing, the solder cream transfer surface having a uniformpredetermined thickness is obtained on the pan surface 220, while theexcessive solder cream overflows from both end sides of the levelingsqueegee 224 and is put as an excessive solder cream 32 on the end ofthe pan surface 220. As shown in FIG. 23(d), thereafter, the stirringsqueegee 222 is moved again to the left side in the drawing so that theexcessive solder cream 32 put on the end of the pan surface 220 isscraped toward the central side in the longitudinal direction of thestirring squeegee 222, and is sufficiently stirred in the vicinity ofthe central part of the pan surface 220 and is put again in the samemanner as in FIG. 23(b).

[0209] Thus, even if the stirring squeegee 222 and the leveling squeegee224 are repetitively reciprocated plural times, the solder creamtransfer surface can be stably formed without causing the solder creamto overflow from the pan surface 220 of the transfer unit 210.

[0210] Even though the shape of the stirring squeegee 222 has a simpleplate-shaped structure in which the protrusion 310 is not provided, thetransfer operation can be carried out without causing the solder creamto overflow from the transfer unit 210 if the amount of the solder creamis proper.

[0211] Moreover, the stirring squeegee 222 and the leveling squeegee 224are automatically controlled to be stirred by automatically carrying outthe reciprocating operation for a predetermined time or with thetransfer operation according to the degree of dryness of the soldercream transfer surface. Consequently, the excellent transfer surface canbe always exposed continuously.

[0212] Next, description will be given to the structure of the suckingnozzle to be attached to the lower end of the attachment head.

[0213] FIGS. 24(a) and (b) are views showing the structure of thesucking nozzle, FIG. 24(a) being a front view and FIG. 24(b) being aside view, a part of which is taken away.

[0214] The sucking nozzle 134 includes a rubber pad 322 which has an airsucking passage 320 formed therein, has the sucking surface of the tipportion capable of being inclined and is extendable in the direction ofsuction (a vertical direction in the drawing), and sucking componentcorrecting members 326 a and 326 b to be rod members which are providedin pairs on both sides of the rubber pad 322 and serve to horizontallycorrect the sucking attitude of the electronic component 20 when the tipportions 324 a and 324 b contact on the rear face of the electroniccomponent 20 during the suction of the electronic component 20.

[0215] According to the structure of the sucking nozzle 134, when thesolder cream is to be transferred to the electronic component 20 overthe pan surface 220 of the transfer unit 210 inclined from a horizontalplane as shown in FIGS. 25(a), (b), and (c), it is possible to preventthe electronic component 20 from remaining in the transfer unit 210 dueto the viscosity of the solder cream after the electronic component isimmersed into the solder cream transfer surface of the pan surface 220.More specifically, when the sucking nozzle 134 is slightly brought downin the state in which the electronic component 20 shown in FIG. 25(a)contacts on the pan surface 220 of the transfer unit 210, the electroniccomponent 20 is slanted along the inclination of the pan surface 220 bysetting the tip portion 324 a of the sucking component correcting member326 a to be the center of rotation as shown in FIG. 25(b). Consequently,pressing force is applied from the tip potion 324 a of the suckingcomponent correcting member 326 to the electronic component 20 so thatthe solder cream on the pan surface 220 is uniformly transferred to thelower surface of the electronic component 20. At this time, the rubberpad 322 is maintained to be sucked on the surface of the electroniccomponent 20 and the sucking nozzle 134 maintains such a state that theelectronic component 20 is reliably sucked and held also when theelectronic component 20 shown in FIG. 25(b) is inclined. Also duringpull-up shown in FIG. 25(c), the electronic component 20 is maintainedto be sucked by the rubber pad 322. Therefore, it is possible to preventthe electronic component 20 from being left on the pan surface 220 dueto the viscosity of the electronic component 20 and the solder cream.Consequently, it is possible to reliably pull up the electroniccomponent 20 which is maintained to be sucked and held.

[0216] Similarly, the electronic component mounted on a surface inclinedfrom the horizontal plane as shown in FIGS. 26(a), (b), and (c) can alsoreliably carry out the sucking operation without leaking air. Morespecifically, in the initial state brought before the suction of theelectronic component as shown in FIG. 26(a), the height of the lowersurface of the rubber pad 322 is set to be smaller than the height ofthe tip portion 324 of each of the sucking component correcting members326 a and 326 b by h_(a). Consequently, in the case in which theelectronic component 20 inclined as shown in FIG. 26(b) is to be sucked,the lower surface of the rubber pad 322 first comes in point contactwith the electronic component 20 with the fall of the sucking nozzle 134and the rubber pad 322 is elastically deformed and is thereby suckedonto the surface of the inclined electronic component in face contact.At this time, the amount of elastic deformation in the direction ofsuction of the rubber pad 322 is controlled by the height of the tipportion 324 a of the sucking component correcting member 326 a.

[0217] When the sucking nozzle 134 is pulled up in this state, theelectronic component 20 is lifted upward by the sucking force of therubber pad 322 as shown in FIG. 26(c) and contacts on the tip portion324 b of the sucking component correcting member 326 b so that theelectronic component 20 is sucked and held horizontally.

[0218] Thus, since the sucking nozzle 134 includes the rubber pad, whichis deformable in the direction of the suction, and the sucking componentcorrecting member 326, the electronic component 20 can be sucked stably.Also during the transfer of the solder cream, the rubber pad 322 absorbsan inclination even if the pan surface 220 of the transfer unit 210 isinclined. Therefore, the solder cream can be transferred uniformly tothe lower surface of the electronic component 20. Moreover, theelectronic component 20 is not left on the transfer unit 210 also duringthe pull-up.

[0219] The contact face of the lower surfaces of the tip portions 324 aand 324 b of the sucking component correcting members 326 a and 326 bare inclined from the horizontal plane such that a desirable inclinationangle can be obtained during the suction of the electronic component 20.Consequently, the electronic component can be sucked and held with aninclination having an optional angle and the solder cream can betransferred stably over the inclined pan surface 220 of the transferunit 210. Moreover, the electronic component mounted on the inclinedsurface can also be sucked reliably.

[0220] The sucking component correcting members 326 a and 326 b canincrease a space between the tip portions 324 a and 324 b as shown inFIG. 27 according to the type of the electronic component to be sucked,for example. More specifically, the sucking component correcting members326 a and 326 b are turned over in the state shown in FIGS. 24(a) and(b) and are thus attached so that the space between the tip portions 324a and 324 b can be regulated.

[0221] While the rod members have been illustrated as an example of thesucking component correcting members 326 a and 326 b, a toroidal orprism shape may be taken.

[0222] Next, FIGS. 28(a), (b), and (c) show a state in which the soldercream on the pan surface 220 of the transfer unit 210 is transferred tothe electronic component by using the sucking nozzle 134. FIG. 28(a)shows a state in which the electronic component 20 is sucked into eachsucking nozzle 134 of the attachment heads 138 a to 138 d and thetransfer head is moved above the transfer unit 210, and FIG. 28(b) showsa state in which each sucking nozzle 134 is simultaneously brought downto such a height as to be immersed in the solder cream transfer surfaceof the transfer unit 210. At this time, the amount of fall of thesucking nozzle 134 is accurately set by adding a difference Δh in aheight between a well-known edge portion and the solder cream transfersurface to a height h_(e) of the edge portion of the transfer unit 210which is measured by a length measuring sensor such as a laserdisplacement sensor which is not shown, thereby calculating a distance(h_(e)+Δh) to the solder cream transfer surface. As shown in FIG. 28(c),thus, the sucking nozzle 134 is pulled up to completely transfer thesolder cream.

[0223] By the transfer of the solder cream, the solder cream 30 is givenin a predetermined amount to the lower surface side of the solder ball26 as shown in an enlarged view of FIG. 29 showing the solder ballobtained after the solder cream is transferred if the electroniccomponent is a BGA, for example. At this time, if a depth at which thesolder ball 26 is pushed in from the solder cream transfer surface is tosmall, the height of the solder ball is not equal. Therefore, the soldercream is not given to all the solder balls or is not given in asufficient amount so that conduction failures might be caused. If thesame depth is too great, the solder cream is excessively given so thatthe solder balls 26 might be short-circuited. For this reason, it ispreferable that the push-in depth of the solder ball should be set tothe following dimension.

[0224] More specifically, FIG. 30 shows the push-in depth of the solderball. If the radius of the solder ball 26 is represented by r, theheight of the solder cream transfer surface is preferably set to aheight ranging from the lowermost point of the solder ball 26 to theradius r, and more preferably, a height of 0.8 r. Consequently, a properamount of the solder cream can be given to the solder ball 26.

[0225] Next, a transfer position on the transfer unit 210 will bedescribed.

[0226] Referring to the solder cream transfer surface formed on the pansurface 220 of the transfer unit 210, basically, when a one-timetransfer operation is completed, the squeegee unit 216 is reciprocatedagain to form a new solder cream transfer surface. However, when aninterval required till the next transfer operation is short, thetransfer operation can be carried out in a position different from thelast transfer position without forming the solder cream transfer surfaceagain. Consequently, a tact for the mounting operation is shortened.

[0227] FIGS. 31(a) and (b) are views showing a state in which thetransfer operation is carried out over the same solder cream transfersurface plural times. A first transfer operation is carried out in aregion A₁ on this side of the solder cream transfer surface as shown inFIG. 31(a) and a second transfer operation is carried out in a region A₂on the inner side of the solder cream transfer surface as shown in FIG.31 (b). P₁ to P₄ shown in the region A₁ represent transfer tracksobtained by the attachment heads 138 a, 138 b, 138 c and 138 d shown inFIG. 28(a). Herein, the four attachment heads 138 a, 138 b, 138 c and138 d are moved vertically at the same time, thereby carrying out thetransfer operation.

[0228] Moreover, FIGS. 32(a) and (b) also show a state in which thetransfer operation is carried out over the same solder cream transfersurface plural times. In this case, as shown in FIG. 32(a), the transferoperation is carried out by the attachment heads 138 a, 138 b, 138 c and138 d in the positions of P₁ to P₄ as shown in FIG. 32(a) and thetransfer operation is then carried out by any of the attachment heads inpositions P₅, P₆ and P₇ adjacent to the positions P₁ to P₄ as shown inFIG. 32 (b). In the drawing, the transfer track in each position isshown. According to each transfer method, the solder cream transfersurface can be utilized effectively.

[0229] Furthermore, FIG. 33 shows a state in which the transferoperation shown in FIGS. 31(a) and (b) and the transfer operation shownin FIGS. 32(a) and (b) are combined to carry out a transfer operation.More specifically, the transfer operation is carried out for this sideand inner side of the solder cream transfer surface and the positionadjacent to each transfer position. Consequently, almost the wholesolder cream transfer surface is used for the transfer operation so thatthe area efficiency of the transfer unit 210 can be enhanced at amaximum.

[0230] Next, description will be given to a three-dimensional mountingmethod of attaching the solder cream transfer apparatus 200 to theelectronic component mounting apparatus 100, thereby mounting anelectronic component on a circuit board in multi-stages.

[0231] FIGS. 34(a), (b) and (c) are views showing the appearance of theelectronic component 20(22) to be three-dimensionally mounted, (a) beinga plan view, (b) being a side view and (c) being a bottom view. In thethree-dimensional mounting method, the electronic component 20 ismounted on the circuit board 10 and is then mounted on the rear face ofthe electronic component 20 which has already been mounted. Thus, spacesaving can be attained by polymerizing a mounting space on the circuitboard 10 for the electronic component 22 with the mounting space of theelectronic component 20.

[0232] A detailed procedure for the three-dimensional mounting methodwill be sequentially described below with reference to FIGS. 35(a), (b),(c), (d), (e), (f), (g), and (h).

[0233] First of all, in FIG. 35(a), the electronic component 20 ismounted on the circuit board 10 such that the land position iscoincident with the position of the solder ball (a first mounting step).The circuit board 10 has the land 24 formed in a position correspondingto each solder ball 26 of the electronic component 20. In this case, aboard mark for position recognition on the circuit board 10 which is notshown is detected by the recognizing camera 135, thereby grasping anaccurate land position and aligning the electronic component 20 withhigh precision.

[0234] In FIG. 35(b), next, the electronic component 20 is mounted onone of the surfaces of the circuit board 10 and is then subjected to areflow process. Thus, the solder cream is molten to connect the land 24to the solder ball 26 electrically and mechanically and to fix theelectronic component 20 onto the circuit board 10 (a first reflow step).

[0235] As shown in FIG. 35(c), subsequently, the circuit board 10 isturned over and the electronic component 20 is mounted on the reversesurface of the circuit board 10 (a second mounting step). As shown inFIG. 35(d), then, the circuit board 10 having the electronic component20 mounted on a right side surface and the electronic component 20 fixedto a reverse side surface is subjected to the reflow process, therebyfixing the electronic component 20 on the right side surface onto thecircuit board 10 in the same manner (a second reflow step).

[0236] By these steps, a double-sided mounting board is obtained. In thetwo-dimensional mounting method, the following step is added. Morespecifically, as shown in FIG. 35(e), the electronic component 22 havinga solder cream transferred to a solder ball is stacked and mounted onthe upper surface of the electronic component 20 of the circuit board 10which has been subjected to the second reflow step (a third mountingstep).

[0237] As shown in FIG. 35(f), next, the circuit board 10 thus stackedand mounted is subjected to a reflow process (a third reflow step). Asshown in FIG. 35(g), furthermore, the circuit board 10 is turned overand the electronic component 22 is mounted on the upper surface of themounted electronic component 20 in the same manner as in the thirdmounting step (a fourth mounting step). As shown in FIG. 35(h), thecircuit board 10 is subjected to the reflow process (a fourth reflowstep).

[0238] By repeating the steps subsequent to the third mounting step, theelectronic component 20 (22) can be provided on the circuit board 10 inmulti-stages. In order to carry out the reflow process over only aportion to be a reflow object on the circuit board 10, for example, ahot blast is blown against the right side surface of the circuit board10 and a cold blast is blown against the back side surface, or the sizeof the solder ball 26 of the electronic component 20 provided on theupper layer of an electronic component to be stacked is reduced (a heatcapacity is reduced). Thus, well-known means is preferably usedtogether.

[0239] Moreover, while the BGA has been taken as an example of theelectronic component 20 (22), it is not restricted but such a structureas to stack a QFP, an SOP and an SOJ (Small Out-line J-Leaded Package)on the BGA in addition to the CSP may be employed.

[0240] In order to prevent melting when carrying out the reflow processplural times, the solder ball 26 of the electronic component 20 may beconstituted by a combination of a cylindrical pin and a solder ball.More specifically, as shown in an example of FIG. 36, it is preferablethat a heat-resistant pin 28 as in a general PGA (Pin Grid Array) shouldbe provided as a terminal and the solder 29 should be fixed to the pin28. According to such a structure, the solder 29 is molten and issolidified around the pin 28 to have a wettability in the state of aconnecting terminal portion which is obtained after the reflow processin FIG. 37, and a shortage of the length of the solder 29 is absorbed sothat the solder 29 is reliably connected to the land 24 even if thelength of the pin 28 is not equal. More specifically, in the case inwhich a clearance between the circuit board 10 and the pin 28 is great,the fixed solder is molten and filled in the clearance. If the clearanceis small, a large amount of the solder sticks to the peripheral surfaceof the pin 28. Moreover, the lower end of the pin 28 is caused to beflat so that the electronic component 20 can be stably fixed withoutinclining an attitude thereof from the circuit board surface.Furthermore, even if the solder 29 is exposed to a high heat by thereflow process again, it maintains to stick to the periphery of the pin28 by a surface tension. Therefore, the electrodes can be prevented frombeing short-circuited.

[0241] Furthermore, it is preferable that the alignment of theelectronic components in the three-dimensional mounting method should becarried out as shown in FIGS. 38(a), (b), (c), and (d). FIGS. 38(a),(b), (c), and (d) are views showing a procedure for aligning theelectronic component on a stepwise basis, a plan view and a side viewbeing illustrated together.

[0242] As shown in FIG. 38(a), first of all, the recognizing camera 135detects board marks 40 and 40 for alignment provided on the circuitboard 10. The board mark 40 is provided in a diagonal line position ofan opposite side of the circuit board 10, for example, and therespective board marks 40 and 40 are detected to recognize theinclination and rotation component of the circuit board 10. As shown inFIG. 38(b), the amount of movement of the attachment head and the amountof rotation of the sucking nozzle are controlled corresponding to theresult of the recognition, thereby correcting the position and mountingthe electronic component 20 on the circuit board 10. Next, theelectronic component 20 is mounted on the upper surface of the mountedelectronic component 20. In that case, reference marks 42 and 42 foralignment are provided on the rear face of the electronic component 20to be mounted, and the reference marks 42 and 42 are detected, therebycorrecting the position. More specifically, by detecting the referencemarks 42 and 42 on the rear face of the electronic component 20 by therecognizing camera 135 after mounting the electronic component 20 asshown in FIG. 38(c), the mounting positional shift of the mountedelectronic component 20 is detected, and the electronic component 22 ina second stage is aligned and mounted on the rear face of the electroniccomponent 20 as shown in FIG. 38(d) to cancel the mounting positionalshift of the electronic component 20 thus detected.

[0243] Thus, the reference mark 42 for alignment is provided on the rearface of the electronic component 20. Consequently, the solder ball 26 ofthe electronic component 22 in the second stage can be stacked with highalignment precision in the position of a land 25 provided on the rearface of the electronic component 20 which has been mounted on thecircuit board 10, and can be thus mounted on the rear face of thecomponent having high precision.

[0244] At this time, while the board mark 40 on the circuit board 10 andthe reference mark 42 on the electronic component 20 may be picked up bythe same recognizing camera 135, the marks 40 and 42 having differentheights may be picked up by switching a plurality of recognizing camerashaving different focusing positions. Consequently, it is not necessaryto regulate the height of the recognizing camera 135 and the focusingdistance of the lens. Thus, the mark detection can be carried outrapidly.

[0245] Next, description will be given to a solder cream cleaning workfor the solder cream transfer apparatus 200.

[0246] The squeegee unit 216 of the solder cream transfer apparatus 200is to be cleaned for removing a solder cream when there is a possibilitythat the solder cream used at a last time and sticking to each squeegeemight be solidified at the time of the start of the operation of thesolder cream transfer apparatus 200. It is advantageous that thesqueegee unit 216 is removed from the transfer unit 210 to carry out thecleaning work in respect of an enhancement in workability. However, itis necessary to carry out the cleaning work with high reproducibilityprecision in the attachment position of each component during anassembly. Therefore, it has conventionally been hard to obtain such astructure as to be cleaned rapidly.

[0247] In the structure of the solder cream transfer apparatus 200according to the embodiment, the squeegee unit 216 is set to be of aremoval type having a high cleaning work efficiency and to have astructure with high reproducibility of assembly precision in order toeasily carry out the cleaning work for the solder cream. The procedurefor the cleaning work of the solder cream transfer apparatus 200 will besequentially described below.

[0248] First of all, two screws 270 of the squeegee unit 216 shown inFIGS. 12(a) and (b) are loosened and an upper V block 268 supporting oneof ends is removed. Next, a screw 282 fixing an engagement portion 274of the squeegee fixing member 250 on the other end shown in FIGS. 13(a)and (b) is loosened to remove the squeegee fixing member 250 shown inFIG. 9 from the housing 214. Consequently, the squeegee unit 216 istaken out in the state of a single body shown in FIG. 11. Then, thesolder cream sticking to the squeegee surface of the squeegee unit 216is removed to carry out cleaning such that the solidified solder creamis not left.

[0249] Then, the cleaned squeegee unit 126 from which the solder creamis removed is attached such that a key groove 276 of the engagementportion 274 is fitted in a projection 278 of the receiving table 280reversely to the removal and the screw 282 is temporarily fixed. Next,an embedded pin 262 provided in the squeegee fixing member 250 is heldto attach the upper V block 268 to a lower V block 266 with a screw 270and each of the screws 282 and 270 is fastened.

[0250] Thus, one of the ends of the squeegee fixing member 250 isconstrained by the fitting of the key groove 276 of the engagementportion 274 and the other end is supported on the V block so that thefixation can be carried out without twisting the squeegee fixing member250. For this reason, the squeegee tips of the stirring squeegee 222 andthe leveling squeegee 224 can be provided on the pan surface 220 of thetransfer unit 210 with high parallelism and high positional precision.

[0251] As described above, according to the solder cream transferapparatus 200 in accordance with the embodiment, the stirring squeegeestirs the solder cream over the transfer unit on the going path of thetransfer unit and the leveling squeegee sets the solder cream stirred onthe going path to have a predetermined thickness on the returning pathof the transfer unit. As a result, a flat solder cream transfer surfaceis formed on the transfer unit. At this time, a protrusion for scrapingthe solder cream on the pan surface toward the central side in thelongitudinal direction of the stirring squeegee is formed on the pansurface side of both ends in the longitudinal direction of the stirringsqueegee. When the stirring squeegee is to be relatively moved againafter the relative movement of the leveling squeegee, consequently, thesolder cream overflowing from both ends in the longitudinal direction ofthe leveling squeegee during the relative movement of the levelingsqueegee at the last time can be scraped toward the central side in thelongitudinal direction of the squeegee by a formed discharge portion.Therefore, it is possible to prevent the solder cream from overflowingfrom the pan surface of the transfer unit.

[0252] According to the electronic component mounting apparatus 100 inaccordance with the embodiment, moreover, a desirable electroniccomponent is sucked and held through the sucking nozzle from anelectronic component supply member having a plurality of electroniccomponents mounted thereon and is positioned on the transfer unit of thesolder cream transfer apparatus by moving the attachment head throughthe head moving portion. Then, the attachment head is brought up anddown to immerse the terminal portion of the electronic component in thesolder cream transfer surface on the transfer unit and to transfer thesolder cream to the electronic component. Consequently, the solder creamcan be uniformly transferred to the electronic component so that theelectronic component can be mounted into a predetermined position.

[0253] Furthermore, the electronic component (semiconductor device) tobe used for the electronic component mounting apparatus according to theembodiment is provided with the land for terminal connection in aposition corresponding to the connecting terminal of the electroniccomponent on the rear face side of the electronic component.Consequently, the land of the electronic component on the lower stageside and the connecting terminal of the electronic component on theupper stage side are aligned to stack the electronic components so thatthe stack structure of the electronic components can be obtained. Thus,the mounting efficiency of the electronic component can be enhanced sothat the mounting can be carried out at a higher density.

[0254] While the electronic component mounting apparatus 100 for movingthe transfer head 128 in an X-Y plane has been described as an examplein the embodiment, it is not restricted but an electronic componentmounting apparatus of a rotary type may be used. The electroniccomponent mounting apparatus of the rotary type has a head constitutedby a cylindrical cam and serves to position and move ten stations, forexample, and to move and position the circuit board into a predeterminedposition over the X-Y table, thereby mounting the electronic component.

[0255] Moreover, the solder cream transfer apparatus 200 can transfer aviscous fluid such as a flux, a silver paste or a conductive paste inaddition to the transfer of the solder cream.

[0256] Next, description will be given to a second embodiment of theviscous fluid transfer apparatus according to the invention.

[0257] The viscous fluid (solder cream) transfer apparatus according tothe embodiment has the feature of the tip shape of the leveling squeegeeof the squeegee unit 216.

[0258] More specifically, a leveling squeegee 290 according theembodiment has a flat and elongated shape in the same manner as that inthe first embodiment and a tip portion is formed to have a simpleV-shaped cut in FIG. 39 showing the enlarged tip portion. According tothe leveling squeegee, an excessive solder cream is dropped downward andreturned at a corner portion 290 a. Consequently, the solder cream canbe prevented from being transmitted to the upper part of the squeegee290. Moreover, the simple V-shape can reduce the manufacturing cost ofthe squeegee.

[0259] According to a variant of the embodiment, furthermore, the shapeof a leveling squeegee shown in FIGS. 40(a) and (b) may be employed. Thetip potion of the leveling squeegee 292 is provided with a cornerportion 292 a having a V-shaped cut, and furthermore, a corner portion292 b having an obtuse section and protruded outward is formed in thelongitudinal direction of the squeegee in the middle of an inclinedsurface in the forward part in the direction of progress of thesqueegee. Accordingly, the corner portions 292 a, 292 b and 292 c areformed in the direction of progress of the squeegee from the tip portionof the squeegee.

[0260] According to the leveling squeegee 292, as shown in FIG. 40(a)illustrating the state of the movement of the squeegee, the solder creamis pressurized and extended by the corner portion 292 a to form a layerhaving a uniform solder cream thickness, and the excessive solder creamis stirred along the inclined surface between the corner portion 292 aand the corner portion 292 b and is dropped downward and returned at thecorner portion 292 b. Even if the excessive solder cream is transmittedupward from the corner portion 292 b, the solder cream is droppeddownward and returned by the corner portion 292 c as shown in FIG.40(b). Thus, it is possible to reliably prevent the solder cream frombeing transmitted to the upper part of the squeegee 292. Thus, thestirred solder cream is always put in a uniform thickness.

[0261] Next, description will be given to a third embodiment of theviscous fluid transfer apparatus according to the invention.

[0262] The viscous fluid (solder cream) transfer apparatus according tothe embodiment is provided with a pressure generating member 296 forstably putting a solder cream in the vicinity of the tip of a levelingsqueegee 294 of the squeegee unit 216. FIG. 41 is a side view showingthe structure of the attachment of the pressure generating member 296.The leveling squeegee 294 and the pressure generating member 296 aresupported independently so that relative attachment positions thereofcan be regulated.

[0263] The pressure generating member 296 has a rod body taking acircular section and is attached to a bracket which is not shown, and issupported in parallel with the leveling squeegee 294 in the longitudinaldirection of the leveling squeegee 294 in the vicinity of the tip of theleveling squeegee 294. Moreover, the pressure generating member 296 isformed of a high rigid material such as a metal, ceramics or hardplastics and reduces the generation of a flex.

[0264] The squeegee 294 forms a narrow path 298 having a small clearanceS between the pressure generating member 296 and the pan surface 220 ofthe transfer unit 210, and a passage 299 having a clearance T to be apassage for the solder cream to be rolled is also formed between thepressure generating member 296 and the squeegee 294. The clearances Sand T of the narrow passage 298 and the passage 299 are set to rangefrom approximately 1 mm to 3 mm, for example.

[0265] By providing the pressure generating member 296 forming theclearances S and T, the solder cream to be rolled with the movement ofthe squeegee 294 which passes through the narrow passage 298 and thepassage 299 is brought in a higher pressure state than in other regions.As a result, the solder cream is pushed uniformly and stably to theclearance between the squeegee 294 and the pan surface 220 of thetransfer unit 210 so that a solder cream transfer surface having a moreuniform thickness can be formed. Moreover, even if a squeegee speed ishigh, the solder cream can be put on the pan surface 220 stably in apredetermined thickness.

[0266] The shape of the pressure generating member 296 is not restrictedto a rod but various shapes such as a semispherical sectional shape or awedge sectional shape may be utilized. Moreover, the pressure generatingmember 296 is provided such that it has a maximum height h_(max) fromthe pan surface 220 of the transfer unit 210 than a rolling height h_(r)of the solder cream during the formation of the solder cream transfersurface and it is embedded in the solder cream during the rolling.

[0267] Furthermore, the pressure generating member 296 according to theembodiment may be provided in the stirring squeegee 222 so that thestirring effect can be enhanced still more.

[0268] Next, description will be given to a fourth embodiment of theviscous fluid transfer apparatus according to the invention.

[0269] The viscous fluid (solder cream) transfer apparatus according tothe embodiment has such a structure that a protrusion to be formed inthe stirring squeegee of the squeegee unit 216 is provided in pluralportions between both ends of the squeegee and the apparatus.

[0270] FIGS. 42(a) and (b) shows the shape of a stirring squeegee 340according to the embodiment, FIG. 42(a) being a front view and FIG.42(b) being a side view. Moreover, FIG. 43 is a sectional view takenalong F-F in FIGS. 42(a) and (b). A portion shown in a slant line ofFIG. 42(b) indicates the lowermost surface of the stirring squeegee 340.

[0271] As shown in FIGS. 42(a), 42(b), and 43, the plate-shaped stirringsqueegee 340 has a fixing hole 340 a to the squeegee fixing member 250provided on one of the sides of a long side, and a protrusion 342 havinga triangular longitudinal section provided with a taper face 342 a forscraping the solder cream toward the central side in the longitudinaldirection of the squeegee with the movement of the squeegee is formed onthe pan surface side to be the push side of the solder cream at a lowerend shown in FIG. 42(a) on both ends in the longitudinal direction.Furthermore, a plurality of intermediate protrusions 344 having atriangular longitudinal section is provided between both protrusions 342so that the shape of a comb tooth is taken. The stirring squeegee 340 isused in a forward inclination state in the direction of progress of thesqueegee by a predetermined angle θ_(s). Therefore, the protrusion 342and the intermediate protrusion 344 in the squeegee 340 are cut at theangle θ_(s) as shown in FIG. 43.

[0272] It is preferable that a proper number of intermediate protrusions344 should be provided corresponding to the number of attachment heads138 provided in the transfer head 128. In the embodiment, the fourattachment heads 138 a, 138 b, 138 c and 138 d (see FIGS. 28(a), (b),and (c)) are used. Therefore, three intermediate protrusions 344 areprovided such that solder cream outlets are formed in four lines intotal.

[0273] FIGS. 44(a), (b), (c), and (d) are views illustrating a state inwhich the solder cream transfer surface is formed on the transfer unit210 by using the stirring squeegee 340 according to the embodiment. Thefunction of the stirring squeegee 340 according to the embodiment willbe described with reference to FIGS. 44(a), (b), (c), and (d).

[0274] First of all, as shown in FIG. 44(a), the solder cream 30 ismounted almost uniformly on the pan surface 220 of the transfer unit210. As shown in FIG. 44(b), next, the stirring squeegee 340 accordingto the embodiment is moved toward the left side in the drawing, therebystirring the solder cream 30 and putting the solder cream 30 on the pansurface 220. At this time, a position where the solder cream 30 is to beput is divided by the intermediate protrusion 344 and the solder cream30 is put like a band in four lines in the drawing. In other words, thesolder cream is partially scraped from the pan surface of the transferunit so that the stirring effect can be enhanced still more.

[0275] As shown in FIG. 44(c), furthermore, when the leveling squeegee224 is moved toward the right side in the drawing, the solder creamtransfer surface having a uniform thickness is obtained on the pansurface 220, while the excessive solder cream overflows from both endsides of the leveling squeegee 224 and is put as the excessive soldercream 32 on the end of the pan surface 220. The excessive solder cream32 is scraped toward the central side in the longitudinal direction ofthe stirring squeegee 340 by moving the stirring squeegee 340 againtoward the left side in the drawing in the same manner as that in thefirst embodiment shown in FIGS. 23(a), (b), (c), and (d), and is putagain in such a state as to be sufficiently stirred in the vicinity ofthe central part of the pan surface 220 in the same manner as in FIG.44(b).

[0276] Next, description will be given to a fifth embodiment of theviscous fluid transfer apparatus according to the invention.

[0277] In the viscous fluid (solder cream) transfer apparatus accordingto the embodiment, a plurality of intermediate protrusions 344 providedin the stirring squeegee 340 according to the fourth embodiment has sucha shape that a passage for a solder cream is tapered in the direction ofprogress of the squeegee.

[0278] FIGS. 45(a) and (b) show the shape of a stirring squeegee 350according to the embodiment, FIG. 45(a) is a front view and FIG. 45(b)is a side view. Moreover, FIG. 46 is a sectional view taken along G-G inFIGS. 45(a) and (b).

[0279] As shown in FIGS. 45(a), 45(b), and 46, the stirring squeegee 350is formed to have the shape of a comb tooth in the same manner as in thefourth embodiment and is provided with a fixing hole 350 a to thesqueegee fixing member 250, a protrusion 352 taking a triangularlongitudinal section which has a taper face 352 a formed therein and aplurality of intermediate protrusions 354 having a triangularlongitudinal section. Moreover, the protrusion 352 and the intermediateprotrusion 354 in the squeegee 350 are cut at an angle θ_(s) as shown inFIG. 46. The intermediate protrusion 354 is formed with a taper face 354a for scraping a solder cream toward the central side of each clearancewith the movement of the squeegee between the protrusion 352 and theintermediate protrusion 354 and between the intermediate protrusions 354as shown in FIG. 45(b). As shown in FIG. 45(b) illustrating the end ofthe stirring squeegee 350 in a slant line portion, a lowermost surfaceis formed to have a triangular shape and the taper face 354 is inclinedto be tapered for narrowing the passage for the solder cream in thedirection of progress of the squeegee.

[0280] According to the shape of the stirring squeegee 350 in accordancewith the embodiment, the protrusion 352 and the intermediate protrusion354 which are provided on this side in the direction of progress of thestirring squeegee 350 act as the taper faces 352 a and 354 a inclinedwith respect to the squeegee surface. Therefore, the solder creamsmoothly flows into each clearance. Consequently, it is possible to morereliably prevent the solder cream from overflowing from both ends in thelateral direction of the stirring squeegee 350. Moreover, the passagefor the solder cream flowing in each clearance is narrowed with themovement of the stirring squeegee 350 and the stirring function of thesolder cream becomes much greater.

[0281] Next, description will be given to a sixth embodiment of theviscous fluid transfer apparatus according to the invention.

[0282] In the viscous fluid (solder cream) transfer apparatus accordingto the embodiment, the height of the solder cream transfer surface ofthe solder cream put on the pan surface 220 of the transfer unit 210 ispreset to be a predetermined height from the pan surface 220.

[0283]FIG. 47 is a view showing a state in which the solder cream istransferred according to the embodiment, illustrating the relationshipbetween the solder cream 30 put on the pan surface 220 of the transferunit 210 and the solder ball 26 of the electronic component 20 suckedinto the sucking nozzle 134. More specifically, a height h_(c) of thetransfer surface of the solder cream put on the pan surface 220 of thetransfer unit 210 according to the embodiment is set to be such a heightthat the solder ball 26 of the electronic component 20 is immersed at aheight which is equal to or smaller than a radius r, preferably, aheight of 0.8 r or less when the sucking nozzle 134 sucking theelectronic component 20 is pushed against the pan surface 220.

[0284] In this case, the height h_(c) of the transfer surface of thesolder cream is determined by the clearance between the tip portion ofthe leveling squeegee 224 and the pan surface 220 of the transfer unit210 and the height h_(c) is controlled by regulating the height of theleveling squeegee 224. More specifically, during initial regulation, thescrew 234 of the arm stopper 232 shown in FIG. 7 is protruded downwardsuch that the leveling squeegee 224 is caused to rise by the heighth_(c) from the pan surface 220 of the transfer unit 210. Consequently,the rocking control arm 226 d contacts on the tip of the screw 234during the rocking operation of the rocking arm 226 so that a heightfrom the pan surface 220 of the leveling squeegee 224 is held by h_(c).

[0285] By such a simple operation as to set the height h_(c) of thetransfer surface of the solder cream to be a defined height and to pushthe sucking nozzle 134 against the pan surface 220 until the terminalportion of the electronic component 20 contacts on the pan surface 220of the transfer unit 210, thus, the solder cream can be given in aproper amount to the electronic component 20.

[0286] Next, description will be given to a seventh embodiment of theviscous fluid transfer apparatus according to the invention.

[0287] The viscous fluid (solder cream) transfer apparatus according tothe embodiment is provided with a stepped portion for suspending theleveling squeegee 224 and causing the same to rise upward such that theheight of the solder cream transfer surface can be always constant whenthe solder cream is to be put on the pan surface of the transfer unit.

[0288]FIG. 48 shows the section of a transfer unit 360 and the levelingsqueegee 224 to slidably come in contact with the transfer unit 360according to the embodiment. A stepped portion 362 for raising theleveling squeegee 224 by the height h_(c) is protruded from the pansurface 364 and is provided in the direction of the movement of thesqueegee on both ends in the direction of squeegee delivery of thetransfer unit 360 according to the embodiment. The lower tip portion ofthe leveling squeegee 224 slidably comes in contact with the steppedportion 362 so that the solder cream is extended by the clearance havingthe height h_(c) which is formed between the leveling squeegee 224 andthe pan surface 364 of the transfer unit 360. Accordingly, the soldercream is formed in a uniform thickness (height h_(c)) and the soldercream transfer surface parallel with the pan surface 364 is stablyformed.

[0289]FIG. 49 shows a state in which the solder cream is transferred tothe electronic component 20 sucked by the sucking nozzle 134 over theformed solder cream transfer surface. As shown in FIG. 49, the suckingnozzle 134 is pushed against the pan surface 364 until the terminalportion (solder ball 26) of the electronic component 20 contacts on thepan surface 364 of the transfer unit 360 so that the solder cream isgiven in a proper amount to the electronic component 20. The heighth_(c) is set to the radius r of the solder ball 26 or less, preferably aheight of 0.8 r from the lower end of the solder ball 26. While theleveling squeegee 224 according to the first embodiment can be used, itis not restricted but a structure may be simplified by using a simpleplate-shaped squeegee.

[0290] Moreover, the transfer unit 360 according to the embodiment maybe constituted to have a deep bottom. In this case, a stepped portion isused for simply flattening the solder cream transfer surface. Morespecifically, as shown in FIG. 50, a stepped portion 372 is provided ina higher position than the radius r of the solder ball 26 from a pansurface 374 of a transfer unit 370 and the lower tip portion of theleveling squeegee is caused to contact on the stepped portion 372 and ismoved so that a flat solder cream transfer surface which is face alignedwith the stepped portion 372 is obtained. The sucking nozzle 134 isbrought down toward the obtained solder cream transfer surface such thatthe solder ball 26 of the electronic component 20 is immersed in thesolder cream by the predetermined height h_(c), in more detail, up to aheight which is equal to or smaller than the radius r of the solderball, preferably up to the height of 0.8 r or less from the lower end ofthe solder ball 26. Consequently, the solder cream is given in a properamount to the electronic component 20. At this time, the amount of thefall of the sucking nozzle 134 is accurately set by previously detectinga height h_(s) of the stepped portion 372 through a length measuringsensor, for example.

[0291] According to such a structure, the solder cream is put in asufficient amount over the transfer unit 370. Therefore, the soldercream is dried more slowly than that in the case in which the soldercream is extended thinly, and a cycle of automatic stirring control canbe set to be longer so that the solder cream transfer surface can beheld easily.

[0292] Moreover, FIG. 51 shows a structure in which a stepped portion isprovided in the leveling squeegee as a variant of the embodiment. Asshown in FIG. 51, a stepped portion 382 protruded by the height of h_(c)is formed on both ends of the leveling squeegee 380 according to thevariant. Consequently, when the stepped portion 382 is caused to contacton the pan surface 220 of the transfer unit 210, a clearance having theheight of h_(c) is formed between the pan surface 220 and a lower tipportion 384 of the leveling squeegee 380. In this case, the samestructure of the transfer unit 210 as that in the first embodiment canbe used.

[0293] By using the leveling squeegee 380, the solder cream 30 caneasily be put on the pan surface 220 of the transfer unit 210 at thedesirable height h_(c) from the clearance. As shown in FIG. 52illustrating the state of the transfer of the solder cream, theelectronic component 20 is pushed against the formed solder creamtransfer surface so that the solder cream can be given in a properamount to the electronic component 20.

[0294] According to the structures in accordance with the embodiment andthe variant thereof, it is not necessary to finely control the heightsof the leveling squeegees 224 and 380 through the arm stopper 232 shownin FIG. 7. Consequently, the control work can be simplifiedconsiderably. In other words, by pushing the leveling squeegee 224against the stepped portions 362 and 372 of the transfer units 360 and370, and furthermore, by pushing the stepped portion 382 of the levelingsqueegee 380 against the pan surface 220 of the transfer unit 210, it ispossible to easily obtain the structure without requiring the finecontrol of the clearance having a predetermined height between theleveling squeegee and the pan surface of the transfer unit. In order tochange the thickness of the solder cream transfer surface, it ispreferable that the height of the stepped portion should be varied. Itis preferable that a plurality of leveling squeegees and a plurality oftransfer units formed by somewhat changing the height of the steppedportion should be prepared and selectively combined to have a properlydesirable height according to the type of the electronic component.

[0295] Next, description will be given to an eighth embodiment of theviscous fluid transfer apparatus according to the invention.

[0296] The viscous fluid (solder cream) transfer apparatus according tothe embodiment has such a structure that the pan surface of the transferunit is extended in the direction of the squeegee delivery so that thenumber of times at which a plurality of attachment heads can betransferred at the same time over the same solder cream transfer surfacecan be increased.

[0297]FIG. 53 is a plan view showing a transfer unit 390 of the soldercream transfer apparatus according to the embodiment. In the transferunit 390, a pan surface 392 is formed to have a greater width than adouble of the attachment head arrangement width of a multi-headincluding a plurality of attachment heads such that a simultaneoustransfer operation can be carried out plural times through themulti-head. FIG. 53 shows a structure as an example. In this examplestructure, the four attachment heads can operate to transfersimultaneously as shown in regions A1 and A2 of the solder creamtransfer surface.

[0298] Moreover, while the transfer unit 390 is formed widely and astirring squeegee 394 and a leveling squeegee 396 are also elongated.They are not restricted, but a plurality of squeegees is allowable insuch situation that the plurality of squeegees are combined to besubstantially elongated.

[0299] According to the solder cream transfer apparatus according to theembodiment, thus, the pan surface 392 of the transfer unit 390 is widelyformed so that the simultaneous transfer operation can be carried outthrough the multi-head plural times and the operation for mounting theelectronic component can be executed smoothly to shorten a mountingtact.

[0300] Next, description will be given to a ninth embodiment of theviscous fluid transfer apparatus according to the invention.

[0301] A viscous fluid (solder cream) transfer apparatus 400 accordingto the embodiment has such a structure that a solder cream is stirredand put on the belt surface of a belt conveyer and a new solder creamtransfer surface can be formed continuously.

[0302] First of all, the structure of the solder cream transferapparatus 400 will be described.

[0303]FIG. 54 shows the schematic structure of the solder cream transferapparatus 400 according to the embodiment, FIG. 55 is a sectional viewtaken along H-H in FIG. 54, and FIG. 56 is a partial sectional viewshowing a section taken along I-I in FIG. 54.

[0304] As shown in FIGS. 54 to 56, the solder cream transfer apparatus400 according to the embodiment has a belt type transfer surface formingmechanism 430 arranged in a plurality of lines (four lines in thedrawings). The belt type transfer surface forming mechanism 430comprises a belt conveyer 416 including a flat belt surface 414 havingboth ends provided between pulleys 410 and 412, a motor for rotating thepulley 410 in one direction which is not shown, a stirring mechanism 418for stirring the solder cream 30 by the operation of the belt conveyer416, and a squeegee 420 for putting the solder cream 30 stirred by thestirring mechanism 418 with a uniform thickness over the belt surface414 of the belt conveyer 416.

[0305] The upper surface of the solder cream transfer apparatus 400 isprovided with a top plate 432 which has the same height as that of thesolder cream transfer surface formed on the belt surface 414 of the beltconveyor 416 and has opening windows 432 a, 432 a, . . . formed on thebelt type transfer surface forming mechanisms 430, 430 . . . . Moreover,the upper surface of the end of the solder cream transfer apparatus 400is provided with a solder cream supply port 434 and the apparatus isfilled with the solder cream in a proper amount.

[0306] The motor may collectively rotate the pulley 410 of the belt typetransfer surface forming mechanism 430.

[0307] Next, description will be given to the formation of a soldercream transfer surface and an operation for transferring a solder creamto an electronic component in the solder cream transfer apparatus 400having the structure described above.

[0308] First of all, as shown in FIG. 55, a predetermined amount of thesolder cream is filled in the apparatus through the solder cream supplyport 434 and the motor rotates the pulley 410. Consequently, the beltsurface 414 of the belt conveyer 416 is moved between the pulleys 410and 412 in the direction of an arrow in the drawing. The solder cream 30thus supplied is stirred by the stirring mechanism 418 rotated by thepulley 410 and provided with a plurality of stirring plates in a radialdirection, for example, and is put on the belt surface 414 wound uponthe pulley 410. Then, the solder cream is flatly put in a predeterminedthickness over the belt surface 414 through the squeegee 420 with therotation of the pulley 410.

[0309] A part of the belt surface 414 in a transverse direction isopened by an opening window 434 a of the top plate 432 as shown in FIGS.54 and 56 and the solder cream is flatly put on the belt surface 414provided just below the opening. Moreover, the solder cream is put tohave almost the same height as the thickness of the top plate 432. Whenthe pulley 410 is continuously rotated, the belt surface 414 is moved sothat a solder cream transfer surface having a predetermined thickness iscontinuously formed.

[0310] Next, the electronic component 20 sucked into the sucking nozzle134 of the attachment head is pushed against the formed solder creamtransfer surface to carry out the operation for transferring the soldercream. FIGS. 57(a), (b), and (c) show, on a stepwise basis, theprocedure for transferring the solder cream to the electronic componentthrough the solder cream transfer apparatus 400 according to theembodiment.

[0311] In the transfer of the solder cream, first of all, informationabout a height to the top plate 432 in the vicinity of the solder creamtransfer surface is detected by a length measuring sensor 436 such as alaser displacement sensor provided on the side of the sucking nozzle 134as shown in FIG. 57(a) and the sucking nozzle 134 is moved just abovethe solder cream transfer surface as shown in FIG. 57(b), and thesucking nozzle 134 is then brought down to transfer the solder cream 30to the electronic component 20 based on the height information obtainedfrom the length measuring sensor 436 as shown in FIG. 57(c).

[0312] According to the solder cream transfer apparatus 400 inaccordance with the embodiment, the solder cream transfer surface isformed continuously in a predetermined position. Therefore, the transferposition where the electronic component is pushed is not changed foreach transfer operation but a new solder cream transfer surface isalways exposed continuously. Consequently, it is possible to simplifythe operation for transferring the solder cream and to shorten amounting tact.

[0313] According to the viscous fluid transfer apparatus in accordancewith the invention, there are provided a transfer unit having a planarpan surface for putting a viscous fluid thereon, a squeegee unit havinga planar stirring squeegee for stirring the viscous fluid put on the pansurface, a planar leveling squeegee for uniformly flattening the viscousfluid thus stirred, and a squeegee fixing member serving to separate thesqueegees from each other and to fix them in parallel and having bothends rockably supported pivotally above the transfer unit, a transferunit moving mechanism for reciprocating the transfer unit such that thesqueegee is relatively moved along the pan surface of the transfer unit,and a squeegee driving mechanism for rocking the squeegee unit such thatthe stirring squeegee and the leveling squeegee approach the pan surfaceon going and returning paths, respectively. Consequently, the stirringsqueegee stirs the viscous fluid put on the transfer unit on the goingpath of the transfer unit and the leveling squeegee uniformly flattensthe viscous fluid stirred on the going path to have a predeterminedthickness on the returning path of the transfer unit. Thus, it ispossible to form a flat viscous fluid transfer surface on the transferunit.

[0314] According to the viscous fluid transfer method in accordance withthe invention, the viscous fluid put on the transfer unit is stirred byrelatively moving the stirring squeegee over the pan surface in aforward direction and the viscous fluid thus stirred is then flatteneduniformly by relatively moving the leveling squeegee over the pansurface in a reverse direction, thereby forming a flat viscous fluidtransfer surface, and the terminal portion of the electronic componentis immersed in the viscous fluid transfer surface to transfer theviscous fluid to the electronic component. By relatively moving the twosqueegees alternately, thus, the flat viscous fluid transfer surface canbe formed stably and the viscous fluid can be uniformly transferred tothe terminal portion of the electronic component.

[0315] According to the electronic component mounting apparatus inaccordance with the invention, there are provided an electroniccomponent supply member for mounting a plurality of electroniccomponents to supply a desirable one of the electronic components, asucking nozzle for removably sucking and holding the electroniccomponent, an attachment head for holding the sucking nozzle to rise andfall freely, a head moving portion for moving the attachment head in ahorizontal plane, and a viscous fluid transfer apparatus for uniformlyflattening a viscous fluid on a transfer unit to form a flat viscousfluid transfer surface, wherein the electronic component sucked by theelectronic component supply member is moved onto the transfer unit ofthe viscous fluid transfer apparatus and a terminal portion of theelectronic component is immersed in the viscous fluid transfer surfaceby the up-down operation of the attachment head, thereby uniformlytransferring the electronic component to the viscous fluid. Thus, theelectronic component to which the viscous fluid is transferred can bemounted in a predetermined position.

[0316] According to the electronic component mounting method inaccordance with the invention, the electronic component is sucked intothe sucking nozzle of the attachment head, while the viscous fluid isuniformly flattened over the transfer unit to form the viscous fluidtransfer surface, thereby moving the sucked attachment head of theelectronic component to the upper position of the viscous fluid transfersurface. Consequently, the transfer of the viscous fluid is completelyprepared. Next, the sucking nozzle is brought down until the terminalportion of the electronic component is immersed in the viscous fluidtransfer surface so that the viscous fluid is transferred to theterminal portion, and the sucking nozzle is then raised and theattachment head is moved to the predetermined mounting position.Consequently, the electronic component to which the viscous fluid istransferred is positioned in the upper part of the mounting position.The sucking nozzle is brought down, thereby mounting the electroniccomponent having the terminal portion to which the viscous fluid istransferred.

[0317] According to the semiconductor device of the invention having aplurality of solder balls arranged as connecting terminals on a mountingsurface side, wherein a land for terminal connection is provided in aposition corresponding to the connecting terminal of the semiconductordevice on a rear face opposite to the mounting surface side.Consequently, the land of the semiconductor device on the lower stageside and the connecting terminal of the semiconductor device on theupper stage side are connected to each other when the semiconductordevice is stacked. Thus, the semiconductor device can be simplified andcan be constituted as a stacked structure. Thus, the mounting can becarried out at a higher density.

What is claimed is:
 1. A viscous fluid transfer apparatus for forming aflat viscous fluid transfer surface for transferring viscous fluid to aconnecting terminal of an electronic component, said viscous fluidtransfer apparatus comprising: a transfer unit including a planar pansurface for putting a viscous fluid thereon; a squeegee unit including astirring squeegee shaped planar for stirring said viscous fluid put onsaid pan surface, a leveling squeegee shaped planer for uniformlyflattening said viscous fluid which is stirred, and a squeegee fixingmember serving to separate said stirring squeegee and said levelingsqueegee from each other and to fix them in parallel, wherein both endsof said fixing member are supported pivotally and rockably above saidtransfer unit; a transfer unit moving mechanism for reciprocating saidtransfer unit such that said stirring squeegee and said levelingsqueegee are relatively moved each other along said planar pan surfaceof said transfer unit; and a squeegee driving mechanism for rocking saidsqueegee unit such that said stirring squeegee approaches said pansurface on going path of said stirring squeegee and said levelingsqueegee approaches said pan surface on returning path of said levelingsqueegee.
 2. The viscous fluid transfer apparatus according to claim 1,further comprising: protrusions formed on a pan surface side of bothends in a longitudinal direction of said stirring squeegee, wherein saidprotrusions scrape said viscous fluid put on said pan surface toward acentral side in the longitudinal direction of said stirring squeegee. 3.The viscous fluid transfer apparatus according to claim 2, wherein saidprotrusion of said stirring squeegee has a taper face inclined in such amanner as a front side of said taper face in a direction of progress ofsaid stirring squeegee is shorter than a back side of said taper facewithin a thickness of said stirring squeegee, wherein the inclination ofsaid taper face causes a passage for said viscous fluid rearward to benarrow in a back side of a direction of progress of said stirringsqueegee.
 4. The viscous fluid transfer apparatus according to claim 2,further comprising: an intermediate protrusion provided between saidprotrusions on both ends of said stirring squeegee, wherein saidintermediate protrusion forms said viscous fluid put on said pan surfacelike a band.
 5. The viscous fluid transfer apparatus according to claim4, wherein said intermediate protrusion of said stirring squeegee has ataper face inclined in such a manner as a front side of said taper facein a direction of progress of said stirring squeegee is shorter than aback side of said taper face within a thickness of said stirringsqueegee, wherein the inclination of said taper face causes a passagefor said viscous fluid rearward to be narrow in a back side of adirection of progress of said stirring squeegee.
 6. The viscous fluidtransfer apparatus according to claim 1, wherein a concave sectionalcurved portion and a convex sectional curved portion are sequentiallyformed on the pan surface side of the leveling squeegee from the frontpart in the direction of progress of the squeegee.
 7. The viscous fluidtransfer apparatus according to claim 1, wherein a tip on the pansurface side of the leveling squeegee is formed to have a V-shapedsection.
 8. The viscous fluid transfer apparatus according to claim 7,further comprising: a corner portion shaped an obtuse angle and formedin a inclined surface on a front part in a direction of progress of saidleveling squeegee; wherein said corner portion is protruded outward andformed over a longitudinal direction of said leveling squeegee.
 9. Theviscous fluid transfer apparatus according to claim 1, furthercomprising: a pressure generating member provided in a longitudinaldirection of said leveling squeegee in the vicinity of a tip on said pansurface side at the front part in the direction of progress of saidleveling squeegee, wherein said pressure generating member forms anarrow path through which said viscous fluid flows between said pansurface and said pressure generating member, when said leveling squeegeemoves; and wherein said pressure generating member forms a passage forsaid viscous fluid between said leveling squeegee and said pressuregenerating member, while said leveling squeegee is moving.
 10. Theviscous fluid transfer apparatus according to claim 1, wherein a lengthof said stirring squeegee is equal to or greater than a scraping widthof said leveling squeegee.
 11. The viscous fluid transfer apparatusaccording to claim 1, further comprising; stepped portions provided onsaid pan surface of said transfer unit at both ends in a direction thatsaid leveling squeegee is across said transfer unit, and provided alonga direction of the movement of said leveling squeegee, wherein saidstepped portion is protruded from said pan surface by a predeterminedheight in order to support both ends of said leveling squeegee inhanging down.
 12. The viscous fluid transfer apparatus according toclaim 1, further comprising: stepped portions provided on both ends ofsaid leveling squeegee in a longitudinal direction of said levelingsqueegee at said pan surface side, wherein said stepped portion isprotruded by a predetermined height.
 13. The viscous fluid transferapparatus according to claim 1, wherein said squeegee driving mechanismincludes: a rocking arm having a first end fixed to a rocking centershaft of the squeegee fixing member and a second end connected to ahorizontal driving mechanism for rocking the squeegee fixing member; andan arm stopper for contacting on the rocking arm to control a rockingangle of the rocking arm.
 14. The viscous fluid transfer apparatusaccording to claim 1, further comprising: a V block holding saidsqueegee fixing member on a first end side of said squeegee fixingmember; and a table having a projection and supporting said squeegeefixing member on a second end side of said squeegee fixing member bysaid projection, wherein said squeegee fixing member includes: acylindrical pin in an axial direction to one of end side in alongitudinal direction of said squeegee fixing member; and an engagementmember having a key groove parallel with the axial direction is providedon the other end side of said squeegee fixing member, wherein saidprojection engaged with said key groove, and wherein said squeegee unitis supported removably by said V block, said table and said squeegeefixing member.
 15. A viscous fluid transfer apparatus for forming a flatviscous fluid transfer surface in order to transfer a viscous fluid to aconnecting terminal of an electronic component, comprising: a beltconveyer including a planar belt surface on which the viscous fluid isto be put; a squeegee for uniformly flattening the viscous fluid put onthe belt surface by a delivery operation of the belt conveyer; and astirring mechanism provided in a front stage of the squeegee in adirection of delivery of the belt conveyer and serving to stir theviscous fluid on the belt surface.
 16. A viscous fluid transfer methodof forming a flat viscous fluid transfer surface by a squeegee andimmersing a terminal portion of an electronic component in the viscousfluid transfer surface, thereby transferring a viscous fluid to theelectronic component, said method comprising the steps of: putting saidviscous fluid on a transfer unit having a flat pan surface; stirringsaid viscous fluid by a plate-shaped stirring squeegee after saidviscous fluid is put on said transfer unit; and forming a viscous fluidtransfer surface by flattening said viscous fluid uniformly after saidviscous fluid is stirred by a plate-shaped leveling squeegee, whereinsaid stirring squeegee is relatively moved with respect to the pansurface in a forward direction during stirring said viscous fluid, andwherein a plate-shaped leveling squeegee is moved relatively withrespect to the pan surface in a reverse direction during flattening saidviscous fluid.
 17. The viscous fluid transfer method according to claim16, further comprising the step of: scraping said viscous fluid towardto a central side in the longitudinal direction of said levelingsqueegee by said stirring squeegee when said stirring squeegee isrelatively moved with respect to the pan surface in a forward directionagain after forming a viscous fluid transfer surface, wherein saidviscous fluid overflows from both ends in a longitudinal direction ofsaid leveling squeegee when said leveling squeegee is relatively movedwith respect to the pan surface in a reverse direction.
 18. The viscousfluid transfer method according to claim 16, wherein a thickness of saidviscous fluid transfer surface formed on said transfer unit is set byregulating a height of a rise of said leveling squeegee from said pansurface of said transfer unit.
 19. The viscous fluid transfer methodaccording to claim 18, wherein said height of the rise from said pansurface is regulated by causing said leveling squeegee to contact onsaid pan surface of said transfer unit over a whole width and setting aposition of contacting said pan surface to be a reference height. 20.The viscous fluid transfer method according to claim 16, wherein saidthickness of said viscous fluid transfer surface is set by a height ofprotrusion of stepped portions provided on said pan surface side on bothends of said leveling squeegee in the longitudinal direction of saidleveling squeegee.
 21. A viscous fluid transfer method of forming a flatviscous fluid transfer surface by a squeegee and immersing a terminalportion of an electronic component in the viscous fluid transfersurface, thereby transferring a viscous fluid to the electroniccomponent, said method comprising the steps of: putting said viscousfluid on a belt surface of a belt conveyer while said viscous fluid isstirred, and forming a viscous fluid transfer surface caused by levelingsaid viscous fluid flatly by a squeegee with a carriage operation ofsaid belt conveyer, wherein said squeegee is provided above said beltsurface.
 22. An electronic component mounting apparatus for sucking andholding an electronic component and mounting the electronic componentinto a predetermined mounting position, said apparatus comprising: anelectronic component supply device for supplying a plurality ofelectronic components to supply a desirable one of said electroniccomponents; a sucking nozzle for removably sucking and holding saidelectronic component; an attachment head for holding said sucking nozzleto rise and fall freely; a head moving device for moving said attachmenthead in a horizontal plane; and a viscous fluid transfer device forforming a flat viscous fluid transfer surface for transferring viscousfluid to a connecting terminal of an electronic component and foruniformly flattening a viscous fluid on a transfer unit to form a flatviscous fluid transfer surface, wherein said viscous fluid transferdevice including a transfer unit having a planar pan surface for puttinga viscous fluid thereon, a squeegee unit having a stirring squeegeeshaped planar for stirring said viscous fluid put on said pan surface, aleveling squeegee shaped planer for uniformly flattening said viscousfluid which is stirred, and a squeegee fixing member serving to separatesaid stirring squeegee and said leveling squeegee from each other and tofix them in parallel, wherein both ends of said fixing member aresupported pivotally and rockably above said transfer unit, a transferunit moving mechanism for reciprocating said transfer unit such thatsaid stirring squeegee and said leveling squeegee are relatively movedeach other along the planar pan surface of said transfer unit, and asqueegee driving mechanism for rocking said squeegee unit such that saidstirring squeegee approaches said pan surface on going path of saidstirring squeegee and said leveling squeegee approaches said pan surfaceon returning path of said leveling squeegee, wherein said electroniccomponent sucked by said electronic component supply member is movedonto said transfer unit of said viscous fluid transfer device and aterminal portion of said electronic component is immersed in saidviscous fluid transfer surface by said up-down operation of saidattachment head, thereby transferring said viscous fluid to saidelectronic component.
 23. The electronic component mounting apparatusaccording to claim 22, wherein said attachment head includes: a rubberpad provided in a tip portion of said sucking nozzle and having asucking surface which can be inclined freely and can be expanded andcontracted freely in a direction of suction; and a sucking attitudecorrecting member provided around said rubber pad in which a tip portionhas a contact face to contact on a rear face of said electroniccomponent during said suction of the electronic component.
 24. Theelectronic component mounting apparatus according to claim 23, whereinsaid sucking attitude correcting member is constituted of a pair of rodbodies provided on both sides of said rubber pad.
 25. The electroniccomponent mounting apparatus according to claim 23, wherein said contactface of said sucking attitude correcting member is formed to be inclinedfrom a horizontal plane.
 26. The electronic component mounting apparatusaccording to claim 22 further comprising: a multi-head having aplurality of said attachment heads arranged in parallel, and whereinsaid transfer unit of said viscous fluid transfer device including a pansurface having a greater width than that of said multi-head.
 27. Theelectronic component mounting apparatus according to claim 26, whereinthe transfer unit includes a pan surface having a greater width than adouble of the width of the multi-head.
 28. An electronic componentmounting method of mounting an electronic component in a predeterminedmounting position, comprising the steps of: sucking an electroniccomponent by an attachment head having a sucking nozzle, while uniformlyflattening a viscous fluid on a transfer unit having a planar pansurface to form a viscous fluid transfer surface; moving the suckedattachment head of the electronic component to an upper position of theviscous fluid transfer surface; bringing down the sucking nozzle until aterminal portion of the electronic component is immersed in the viscousfluid transfer surface; raising the sucking nozzle after transferringthe viscous fluid to the electronic component and moving the attachmenthead to a predetermined mounting position; and bringing down the suckingnozzle in the mounting position, thereby mounting the electroniccomponent.
 29. The electronic component mounting method according toclaim 28, wherein said sucking nozzles of a multi-head including aplurality of attachment heads arranged in parallel are controlled to bebrought up and down at the same time.
 30. The electronic componentmounting method according to claim 28, wherein a height of said viscousfluid transfer surface of said transfer unit is detected before theviscous fluid is transferred to the electronic component, and an amountof bringing down the sucking nozzle of the attachment head is setaccording to the detected height of said viscous fluid transfer surfaceof said transfer unit.
 31. The electronic component mounting methodaccording to claim 28, wherein said viscous fluid transfer surface isformed in a predetermined thickness on said transfer unit and saidterminal portion of said electronic component is pushed to contact onthe pan surface of the transfer unit, thereby transferring the viscousfluid having the predetermined thickness to the electronic component.32. The electronic component mounting method according to claim 28,wherein the viscous fluid is transferred to a second electricalcomponent, and
 33. The electronic component mounting method according toclaim 32, further comprising the steps of: detecting a reference markfor alignment provided on a rear face of said first electroniccomponent, correcting a mounting position of said second electroniccomponent by setting said reference mark as a reference.
 34. Asemiconductor device comprising a plurality of solder balls arranged asconnecting terminals on a mounting surface side, wherein a land forterminal connection is provided in a position corresponding to theconnecting terminal of the semiconductor device on a rear face oppositeto the mounting surface side.
 35. The semiconductor device according toclaim 34, wherein the connecting terminal of the semiconductor device isformed by such a manner that a solder is fixed to a heat-resistant pin.36. The semiconductor device according to claim 34, wherein a referencemark for alignment is provided on the rear face opposite to the mountingsurface side.